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	$175.71	10.728%	$194.5602	$194.56	$194.55	$194.60
Purchase #2	$115.97	13.587%	$131.7268	$131.73	$131.75	$131.70
Purchase #3	$65.92	8.362%	$71.4322	$71.43	$71.45	$71.40
Purchase #4	$39.96	11.466%	$44.5418	$44.54	$44.55	$44.50
Purchase #5	$125.96	8.223%	$136.3177	$136.32	$136.30	$136.30
Purchase #6	$219.94	6.181%	$233.5345	$233.53	$233.55	$233.50
Purchase #7	$232.57	8.853%	$253.1594	$253.16	$253.15	$253.20
7 purchase totals =	$976.03		$1,065.2726	$1,065.27	$1,065.30	$1,065.20