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	$85.83	11.258%	$95.4927	$95.49	$95.50	$95.50
Purchase #2	$111.35	11.291%	$123.9225	$123.92	$123.90	$123.90
Purchase #3	$48.78	3.316%	$50.3975	$50.40	$50.40	$50.40
Purchase #4	$159.76	7.775%	$172.1813	$172.18	$172.20	$172.20
Purchase #5	$219.96	13.343%	$249.3093	$249.31	$249.30	$249.30
Purchase #6	$172.72	3.488%	$178.7445	$178.74	$178.75	$178.70
Purchase #7	$99.71	8.614%	$108.299	$108.30	$108.30	$108.30
7 purchase totals =	$898.11		$978.3468	$978.34	$978.35	$978.30