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	$222.85	13.736%	$253.4607	$253.46	$253.45	$253.50
Purchase #2	$72.33	12.176%	$81.1369	$81.14	$81.15	$81.10
Purchase #3	$211.30	8.467%	$229.1908	$229.19	$229.20	$229.20
Purchase #4	$232.30	4.558%	$242.8882	$242.89	$242.90	$242.90
Purchase #5	$150.96	12.745%	$170.1999	$170.20	$170.20	$170.20
Purchase #6	$95.82	13.270%	$108.5353	$108.54	$108.55	$108.50
Purchase #7	$34.58	9.385%	$37.8253	$37.83	$37.85	$37.80
7 purchase totals =	$1,020.14		$1,123.2371	$1,123.25	$1,123.30	$1,123.20