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	$245.96	10.804%	$272.5335	$272.53	$272.55	$272.50
Purchase #2	$248.69	4.623%	$260.1869	$260.19	$260.20	$260.20
Purchase #3	$138.29	9.590%	$151.552	$151.55	$151.55	$151.60
Purchase #4	$80.66	6.739%	$86.0957	$86.10	$86.10	$86.10
Purchase #5	$146.94	12.519%	$165.3354	$165.34	$165.35	$165.30
Purchase #6	$99.73	11.574%	$111.2728	$111.27	$111.25	$111.30
Purchase #7	$88.93	12.591%	$100.1272	$100.13	$100.15	$100.10
7 purchase totals =	$1,049.20		$1,147.1035	$1,147.11	$1,147.15	$1,147.10