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	$117.45	9.467%	$128.569	$128.57	$128.55	$128.60
Purchase #2	$71.31	10.682%	$78.9273	$78.93	$78.95	$78.90
Purchase #3	$37.27	6.757%	$39.7883	$39.79	$39.80	$39.80
Purchase #4	$98.58	7.672%	$106.1431	$106.14	$106.15	$106.10
Purchase #5	$111.66	8.353%	$120.987	$120.99	$121.00	$121.00
Purchase #6	$178.67	10.139%	$196.7854	$196.79	$196.80	$196.80
Purchase #7	$100.71	4.830%	$105.5743	$105.57	$105.55	$105.60
7 purchase totals =	$715.65		$776.7744	$776.78	$776.80	$776.80