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	$174.73	6.160%	$185.4934	$185.49	$185.50	$185.50
Purchase #2	$216.26	4.701%	$226.4264	$226.43	$226.45	$226.40
Purchase #3	$102.30	9.116%	$111.6257	$111.63	$111.65	$111.60
Purchase #4	$200.81	11.171%	$223.2425	$223.24	$223.25	$223.20
Purchase #5	$130.31	8.515%	$141.4059	$141.41	$141.40	$141.40
Purchase #6	$145.67	3.704%	$151.0656	$151.07	$151.05	$151.10
Purchase #7	$218.49	3.666%	$226.4998	$226.50	$226.50	$226.50
7 purchase totals =	$1,188.57		$1,265.7593	$1,265.77	$1,265.80	$1,265.70