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	$145.98	9.561%	$159.9371	$159.94	$159.95	$159.90
Purchase #2	$185.59	12.121%	$208.0854	$208.09	$208.10	$208.10
Purchase #3	$82.88	7.560%	$89.1457	$89.15	$89.15	$89.10
Purchase #4	$242.75	6.753%	$259.1429	$259.14	$259.15	$259.10
Purchase #5	$39.41	9.438%	$43.1295	$43.13	$43.15	$43.10
Purchase #6	$70.69	8.197%	$76.4845	$76.48	$76.50	$76.50
Purchase #7	$249.72	11.524%	$278.4977	$278.50	$278.50	$278.50
7 purchase totals =	$1,017.02		$1,114.4228	$1,114.43	$1,114.50	$1,114.30