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	$150.59	11.619%	$168.0871	$168.09	$168.10	$168.10
Purchase #2	$238.88	4.748%	$250.222	$250.22	$250.20	$250.20
Purchase #3	$74.55	7.613%	$80.2255	$80.23	$80.25	$80.20
Purchase #4	$37.41	9.393%	$40.9239	$40.92	$40.90	$40.90
Purchase #5	$185.89	5.186%	$195.5303	$195.53	$195.55	$195.50
Purchase #6	$139.77	13.326%	$158.3958	$158.40	$158.40	$158.40
Purchase #7	$191.36	5.468%	$201.8236	$201.82	$201.80	$201.80
7 purchase totals =	$1,018.45		$1,095.2082	$1,095.21	$1,095.20	$1,095.10