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	$124.25	9.837%	$136.4725	$136.47	$136.45	$136.50
Purchase #2	$245.73	5.164%	$258.4195	$258.42	$258.40	$258.40
Purchase #3	$11.46	12.311%	$12.8708	$12.87	$12.85	$12.90
Purchase #4	$179.65	3.351%	$185.6701	$185.67	$185.65	$185.70
Purchase #5	$201.77	9.855%	$221.6544	$221.65	$221.65	$221.70
Purchase #6	$55.45	10.501%	$61.2728	$61.27	$61.25	$61.30
Purchase #7	$64.37	5.403%	$67.8479	$67.85	$67.85	$67.80
7 purchase totals =	$882.68		$944.2080	$944.20	$944.10	$944.30