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	$149.77	3.514%	$155.0329	$155.03	$155.05	$155.00
Purchase #2	$161.95	6.236%	$172.0492	$172.05	$172.05	$172.00
Purchase #3	$104.98	6.251%	$111.5423	$111.54	$111.55	$111.50
Purchase #4	$182.74	11.854%	$204.402	$204.40	$204.40	$204.40
Purchase #5	$177.29	10.240%	$195.4445	$195.44	$195.45	$195.40
Purchase #6	$28.64	11.142%	$31.8311	$31.83	$31.85	$31.80
Purchase #7	$229.91	12.371%	$258.3522	$258.35	$258.35	$258.40
7 purchase totals =	$1,035.28		$1,128.6542	$1,128.64	$1,128.70	$1,128.50