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	$143.76	7.341%	$154.3134	$154.31	$154.30	$154.30
Purchase #2	$99.55	12.440%	$111.934	$111.93	$111.95	$111.90
Purchase #3	$198.25	10.131%	$218.3347	$218.33	$218.35	$218.30
Purchase #4	$6.62	3.460%	$6.8491	$6.85	$6.85	$6.80
Purchase #5	$40.46	10.660%	$44.773	$44.77	$44.75	$44.80
Purchase #6	$85.98	6.148%	$91.2661	$91.27	$91.25	$91.30
Purchase #7	$122.61	4.801%	$128.4965	$128.50	$128.50	$128.50
7 purchase totals =	$697.23		$755.9668	$755.96	$755.95	$755.90