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	$111.36	6.795%	$118.9269	$118.93	$118.95	$118.90
Purchase #2	$139.75	6.698%	$149.1105	$149.11	$149.10	$149.10
Purchase #3	$235.98	7.240%	$253.065	$253.07	$253.05	$253.10
Purchase #4	$192.33	9.654%	$210.8975	$210.90	$210.90	$210.90
Purchase #5	$5.73	3.783%	$5.9468	$5.95	$5.95	$5.90
Purchase #6	$23.83	5.288%	$25.0901	$25.09	$25.10	$25.10
Purchase #7	$101.91	9.375%	$111.4641	$111.46	$111.45	$111.50
7 purchase totals =	$810.89		$874.5009	$874.51	$874.50	$874.50