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	$133.72	10.768%	$148.119	$148.12	$148.10	$148.10
Purchase #2	$223.75	3.567%	$231.7312	$231.73	$231.75	$231.70
Purchase #3	$78.61	4.401%	$82.0696	$82.07	$82.05	$82.10
Purchase #4	$194.38	9.434%	$212.7178	$212.72	$212.70	$212.70
Purchase #5	$248.91	7.472%	$267.5086	$267.51	$267.50	$267.50
Purchase #6	$137.88	11.463%	$153.6852	$153.69	$153.70	$153.70
Purchase #7	$92.61	3.177%	$95.5522	$95.55	$95.55	$95.60
7 purchase totals =	$1,109.86		$1,191.3836	$1,191.39	$1,191.35	$1,191.40