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	$218.32	4.600%	$228.3627	$228.36	$228.35	$228.40
Purchase #2	$115.67	11.282%	$128.7199	$128.72	$128.70	$128.70
Purchase #3	$14.76	9.255%	$16.126	$16.13	$16.15	$16.10
Purchase #4	$74.32	4.804%	$77.8903	$77.89	$77.90	$77.90
Purchase #5	$196.42	12.191%	$220.3656	$220.37	$220.35	$220.40
Purchase #6	$66.25	9.371%	$72.4583	$72.46	$72.45	$72.50
Purchase #7	$53.82	10.381%	$59.4071	$59.41	$59.40	$59.40
7 purchase totals =	$739.56		$803.3299	$803.34	$803.30	$803.40