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	$139.68	8.721%	$151.8615	$151.86	$151.85	$151.90
Purchase #2	$136.27	10.281%	$150.2799	$150.28	$150.30	$150.30
Purchase #3	$237.95	7.375%	$255.4988	$255.50	$255.50	$255.50
Purchase #4	$154.83	6.635%	$165.103	$165.10	$165.10	$165.10
Purchase #5	$176.53	8.453%	$191.4521	$191.45	$191.45	$191.50
Purchase #6	$171.30	5.846%	$181.3142	$181.31	$181.30	$181.30
Purchase #7	$23.60	8.746%	$25.6641	$25.66	$25.65	$25.70
7 purchase totals =	$1,040.16		$1,121.1736	$1,121.16	$1,121.15	$1,121.30