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	$221.45	13.297%	$250.8962	$250.90	$250.90	$250.90
Purchase #2	$70.62	10.472%	$78.0153	$78.02	$78.00	$78.00
Purchase #3	$8.41	6.296%	$8.9395	$8.94	$8.95	$8.90
Purchase #4	$145.91	13.502%	$165.6108	$165.61	$165.60	$165.60
Purchase #5	$215.29	7.730%	$231.9319	$231.93	$231.95	$231.90
Purchase #6	$114.44	10.445%	$126.3933	$126.39	$126.40	$126.40
Purchase #7	$168.30	3.546%	$174.2679	$174.27	$174.25	$174.30
7 purchase totals =	$944.42		$1,036.0549	$1,036.06	$1,036.05	$1,036.00