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	$159.25	5.320%	$167.7221	$167.72	$167.70	$167.70
Purchase #2	$224.86	6.258%	$238.9317	$238.93	$238.95	$238.90
Purchase #3	$116.28	10.213%	$128.1557	$128.16	$128.15	$128.20
Purchase #4	$145.41	13.555%	$165.1203	$165.12	$165.10	$165.10
Purchase #5	$59.65	3.773%	$61.9006	$61.90	$61.90	$61.90
Purchase #6	$238.84	7.790%	$257.4456	$257.45	$257.45	$257.40
Purchase #7	$189.52	3.550%	$196.248	$196.25	$196.25	$196.20
7 purchase totals =	$1,133.81		$1,215.5240	$1,215.53	$1,215.50	$1,215.40