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	$213.51	4.751%	$223.6539	$223.65	$223.65	$223.70
Purchase #2	$119.28	10.491%	$131.7937	$131.79	$131.80	$131.80
Purchase #3	$93.89	5.852%	$99.3844	$99.38	$99.40	$99.40
Purchase #4	$44.66	7.717%	$48.1064	$48.11	$48.10	$48.10
Purchase #5	$220.51	11.137%	$245.0682	$245.07	$245.05	$245.10
Purchase #6	$136.33	3.341%	$140.8848	$140.88	$140.90	$140.90
Purchase #7	$78.91	3.767%	$81.8825	$81.88	$81.90	$81.90
7 purchase totals =	$907.09		$970.7739	$970.76	$970.80	$970.90