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	$71.61	3.123%	$73.8464	$73.85	$73.85	$73.80
Purchase #2	$62.30	12.767%	$70.2538	$70.25	$70.25	$70.30
Purchase #3	$39.51	10.659%	$43.7214	$43.72	$43.70	$43.70
Purchase #4	$198.77	11.714%	$222.0539	$222.05	$222.05	$222.10
Purchase #5	$147.46	12.785%	$166.3128	$166.31	$166.30	$166.30
Purchase #6	$32.58	7.124%	$34.901	$34.90	$34.90	$34.90
Purchase #7	$98.73	5.108%	$103.7731	$103.77	$103.75	$103.80
7 purchase totals =	$650.96		$714.8624	$714.85	$714.80	$714.90