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	$83.54	9.219%	$91.2416	$91.24	$91.25	$91.20
Purchase #2	$62.89	3.705%	$65.2201	$65.22	$65.20	$65.20
Purchase #3	$120.50	8.803%	$131.1076	$131.11	$131.10	$131.10
Purchase #4	$53.80	11.465%	$59.9682	$59.97	$59.95	$60.00
Purchase #5	$159.96	3.366%	$165.3443	$165.34	$165.35	$165.30
Purchase #6	$231.51	9.404%	$253.2812	$253.28	$253.30	$253.30
Purchase #7	$248.66	3.747%	$257.9773	$257.98	$258.00	$258.00
7 purchase totals =	$960.86		$1,024.1403	$1,024.14	$1,024.15	$1,024.10