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	$145.78	3.523%	$150.9158	$150.92	$150.90	$150.90
Purchase #2	$53.38	10.713%	$59.0986	$59.10	$59.10	$59.10
Purchase #3	$7.29	11.235%	$8.109	$8.11	$8.10	$8.10
Purchase #4	$206.71	10.370%	$228.1458	$228.15	$228.15	$228.10
Purchase #5	$68.67	13.425%	$77.8889	$77.89	$77.90	$77.90
Purchase #6	$160.47	13.775%	$182.5747	$182.57	$182.55	$182.60
Purchase #7	$63.40	12.362%	$71.2375	$71.24	$71.25	$71.20
7 purchase totals =	$705.70		$777.9703	$777.98	$777.95	$777.90