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	$132.26	6.525%	$140.89	$140.89	$140.90	$140.90
Purchase #2	$102.75	8.746%	$111.7365	$111.74	$111.75	$111.70
Purchase #3	$52.83	4.262%	$55.0816	$55.08	$55.10	$55.10
Purchase #4	$182.74	9.505%	$200.1094	$200.11	$200.10	$200.10
Purchase #5	$89.68	11.378%	$99.8838	$99.88	$99.90	$99.90
Purchase #6	$177.28	9.652%	$194.3911	$194.39	$194.40	$194.40
Purchase #7	$202.80	8.720%	$220.4842	$220.48	$220.50	$220.50
7 purchase totals =	$940.34		$1,022.5766	$1,022.57	$1,022.65	$1,022.60