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	$82.54	11.538%	$92.0635	$92.06	$92.05	$92.10
Purchase #2	$97.46	8.438%	$105.6837	$105.68	$105.70	$105.70
Purchase #3	$236.70	4.392%	$247.0959	$247.10	$247.10	$247.10
Purchase #4	$54.74	6.765%	$58.4432	$58.44	$58.45	$58.40
Purchase #5	$11.38	10.231%	$12.5443	$12.54	$12.55	$12.50
Purchase #6	$116.88	7.351%	$125.4718	$125.47	$125.45	$125.50
Purchase #7	$99.80	11.530%	$111.3069	$111.31	$111.30	$111.30
7 purchase totals =	$699.50		$752.6093	$752.60	$752.60	$752.60