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	$37.41	9.422%	$40.9348	$40.93	$40.95	$40.90
Purchase #2	$61.63	9.145%	$67.2661	$67.27	$67.25	$67.30
Purchase #3	$62.43	13.326%	$70.7494	$70.75	$70.75	$70.70
Purchase #4	$97.27	3.126%	$100.3107	$100.31	$100.30	$100.30
Purchase #5	$171.37	13.421%	$194.3696	$194.37	$194.35	$194.40
Purchase #6	$73.77	13.514%	$83.7393	$83.74	$83.75	$83.70
Purchase #7	$202.99	12.399%	$228.1587	$228.16	$228.15	$228.20
7 purchase totals =	$706.87		$785.5286	$785.53	$785.50	$785.50