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	$201.48	11.148%	$223.941	$223.94	$223.95	$223.90
Purchase #2	$169.82	6.669%	$181.1453	$181.15	$181.15	$181.10
Purchase #3	$75.91	10.563%	$83.9284	$83.93	$83.95	$83.90
Purchase #4	$240.55	12.828%	$271.4078	$271.41	$271.40	$271.40
Purchase #5	$247.95	3.133%	$255.7183	$255.72	$255.70	$255.70
Purchase #6	$58.53	6.203%	$62.1606	$62.16	$62.15	$62.20
Purchase #7	$12.38	8.692%	$13.4561	$13.46	$13.45	$13.50
7 purchase totals =	$1,006.62		$1,091.7575	$1,091.77	$1,091.75	$1,091.70