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	$127.27	9.353%	$139.1736	$139.17	$139.15	$139.20
Purchase #2	$209.58	3.800%	$217.544	$217.54	$217.55	$217.50
Purchase #3	$112.94	6.448%	$120.2224	$120.22	$120.20	$120.20
Purchase #4	$127.36	10.289%	$140.4641	$140.46	$140.45	$140.50
Purchase #5	$112.57	3.258%	$116.2375	$116.24	$116.25	$116.20
Purchase #6	$135.59	9.530%	$148.5117	$148.51	$148.50	$148.50
Purchase #7	$221.55	10.568%	$244.9634	$244.96	$244.95	$245.00
7 purchase totals =	$1,046.86		$1,127.1167	$1,127.10	$1,127.05	$1,127.10