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	$99.48	12.109%	$111.526	$111.53	$111.55	$111.50
Purchase #2	$104.43	13.130%	$118.1417	$118.14	$118.15	$118.10
Purchase #3	$225.52	7.815%	$243.1444	$243.14	$243.15	$243.10
Purchase #4	$155.86	7.413%	$167.4139	$167.41	$167.40	$167.40
Purchase #5	$159.87	4.374%	$166.8627	$166.86	$166.85	$166.90
Purchase #6	$124.92	11.414%	$139.1784	$139.18	$139.20	$139.20
Purchase #7	$203.27	7.477%	$218.4685	$218.47	$218.45	$218.50
7 purchase totals =	$1,073.35		$1,164.7356	$1,164.73	$1,164.75	$1,164.70