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	$42.26	9.144%	$46.1243	$46.12	$46.10	$46.10
Purchase #2	$149.37	6.826%	$159.566	$159.57	$159.55	$159.60
Purchase #3	$213.40	12.592%	$240.2713	$240.27	$240.25	$240.30
Purchase #4	$18.51	5.345%	$19.4994	$19.50	$19.50	$19.50
Purchase #5	$247.29	12.369%	$277.8773	$277.88	$277.90	$277.90
Purchase #6	$219.34	9.345%	$239.8373	$239.84	$239.85	$239.80
Purchase #7	$40.72	4.851%	$42.6953	$42.70	$42.70	$42.70
7 purchase totals =	$930.89		$1,025.8709	$1,025.88	$1,025.85	$1,025.90