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	$235.30	7.761%	$253.5616	$253.56	$253.55	$253.60
Purchase #2	$238.59	3.666%	$247.3367	$247.34	$247.35	$247.30
Purchase #3	$64.33	10.375%	$71.0042	$71.00	$71.00	$71.00
Purchase #4	$225.63	9.547%	$247.1709	$247.17	$247.15	$247.20
Purchase #5	$208.75	10.797%	$231.2887	$231.29	$231.30	$231.30
Purchase #6	$55.90	7.107%	$59.8728	$59.87	$59.85	$59.90
Purchase #7	$95.66	4.728%	$100.1828	$100.18	$100.20	$100.20
7 purchase totals =	$1,124.16		$1,210.4177	$1,210.41	$1,210.40	$1,210.50