Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$184.63	6.550%	$196.7233	$196.72	$196.70	$196.70
Purchase #2	$97.61	12.159%	$109.4784	$109.48	$109.50	$109.50
Purchase #3	$224.72	13.224%	$254.437	$254.44	$254.45	$254.40
Purchase #4	$230.37	3.761%	$239.0342	$239.03	$239.05	$239.00
Purchase #5	$188.46	6.513%	$200.7344	$200.73	$200.75	$200.70
Purchase #6	$139.90	5.592%	$147.7232	$147.72	$147.70	$147.70
Purchase #7	$177.61	10.568%	$196.3798	$196.38	$196.40	$196.40
7 purchase totals =	$1,243.30		$1,344.5103	$1,344.50	$1,344.55	$1,344.40