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	$152.35	9.622%	$167.0091	$167.01	$167.00	$167.00
Purchase #2	$153.73	7.426%	$165.146	$165.15	$165.15	$165.10
Purchase #3	$231.66	10.654%	$256.3411	$256.34	$256.35	$256.30
Purchase #4	$95.95	7.810%	$103.4437	$103.44	$103.45	$103.40
Purchase #5	$133.72	10.597%	$147.8903	$147.89	$147.90	$147.90
Purchase #6	$71.65	9.563%	$78.5019	$78.50	$78.50	$78.50
Purchase #7	$133.29	8.183%	$144.1971	$144.20	$144.20	$144.20
7 purchase totals =	$972.35		$1,062.5292	$1,062.53	$1,062.55	$1,062.40