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	$214.34	12.474%	$241.0768	$241.08	$241.10	$241.10
Purchase #2	$36.71	4.448%	$38.3429	$38.34	$38.35	$38.30
Purchase #3	$119.81	9.388%	$131.0578	$131.06	$131.05	$131.10
Purchase #4	$208.29	9.541%	$228.1629	$228.16	$228.15	$228.20
Purchase #5	$200.71	9.187%	$219.1492	$219.15	$219.15	$219.10
Purchase #6	$240.28	3.435%	$248.5336	$248.53	$248.55	$248.50
Purchase #7	$40.99	7.589%	$44.1007	$44.10	$44.10	$44.10
7 purchase totals =	$1,061.13		$1,150.4239	$1,150.42	$1,150.45	$1,150.40