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	$62.96	13.513%	$71.4678	$71.47	$71.45	$71.50
Purchase #2	$84.91	6.522%	$90.4478	$90.45	$90.45	$90.40
Purchase #3	$113.70	13.532%	$129.0859	$129.09	$129.10	$129.10
Purchase #4	$150.82	12.627%	$169.864	$169.86	$169.85	$169.90
Purchase #5	$133.57	8.662%	$145.1398	$145.14	$145.15	$145.10
Purchase #6	$152.90	11.345%	$170.2465	$170.25	$170.25	$170.20
Purchase #7	$235.55	3.275%	$243.2643	$243.26	$243.25	$243.30
7 purchase totals =	$934.41		$1,019.5161	$1,019.52	$1,019.50	$1,019.50