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	$101.98	10.566%	$112.7552	$112.76	$112.75	$112.80
Purchase #2	$180.33	5.611%	$190.4483	$190.45	$190.45	$190.40
Purchase #3	$142.89	11.634%	$159.5138	$159.51	$159.50	$159.50
Purchase #4	$65.85	10.640%	$72.8564	$72.86	$72.85	$72.90
Purchase #5	$134.53	11.648%	$150.2001	$150.20	$150.20	$150.20
Purchase #6	$248.47	5.256%	$261.5296	$261.53	$261.55	$261.50
Purchase #7	$71.58	13.312%	$81.1087	$81.11	$81.10	$81.10
7 purchase totals =	$945.63		$1,028.4121	$1,028.42	$1,028.40	$1,028.40