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	$103.55	7.455%	$111.2697	$111.27	$111.25	$111.30
Purchase #2	$211.91	5.769%	$224.1351	$224.14	$224.15	$224.10
Purchase #3	$43.58	4.654%	$45.6082	$45.61	$45.60	$45.60
Purchase #4	$150.81	12.560%	$169.7517	$169.75	$169.75	$169.80
Purchase #5	$229.77	5.868%	$243.2529	$243.25	$243.25	$243.30
Purchase #6	$117.64	9.286%	$128.5641	$128.56	$128.55	$128.60
Purchase #7	$245.96	12.720%	$277.2461	$277.25	$277.25	$277.20
7 purchase totals =	$1,103.22		$1,199.8278	$1,199.83	$1,199.80	$1,199.90