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	$191.35	4.603%	$200.1578	$200.16	$200.15	$200.20
Purchase #2	$235.90	6.297%	$250.7546	$250.75	$250.75	$250.80
Purchase #3	$150.84	9.510%	$165.1849	$165.18	$165.20	$165.20
Purchase #4	$146.45	9.538%	$160.4184	$160.42	$160.40	$160.40
Purchase #5	$221.85	10.512%	$245.1709	$245.17	$245.15	$245.20
Purchase #6	$177.88	9.303%	$194.4282	$194.43	$194.45	$194.40
Purchase #7	$127.39	12.851%	$143.7609	$143.76	$143.75	$143.80
7 purchase totals =	$1,251.66		$1,359.8757	$1,359.87	$1,359.85	$1,360.00