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	$40.48	5.473%	$42.6955	$42.70	$42.70	$42.70
Purchase #2	$135.55	6.107%	$143.828	$143.83	$143.85	$143.80
Purchase #3	$71.31	10.629%	$78.8895	$78.89	$78.90	$78.90
Purchase #4	$51.25	5.801%	$54.223	$54.22	$54.20	$54.20
Purchase #5	$54.66	13.631%	$62.1107	$62.11	$62.10	$62.10
Purchase #6	$181.64	11.226%	$202.0309	$202.03	$202.05	$202.00
Purchase #7	$144.67	11.677%	$161.5631	$161.56	$161.55	$161.60
7 purchase totals =	$679.56		$745.3407	$745.34	$745.35	$745.30