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	$19.35	5.572%	$20.4282	$20.43	$20.45	$20.40
Purchase #2	$62.81	13.404%	$71.2291	$71.23	$71.25	$71.20
Purchase #3	$172.44	8.718%	$187.4733	$187.47	$187.45	$187.50
Purchase #4	$137.51	6.709%	$146.7355	$146.74	$146.75	$146.70
Purchase #5	$191.91	4.818%	$201.1562	$201.16	$201.15	$201.20
Purchase #6	$174.81	5.176%	$183.8582	$183.86	$183.85	$183.90
Purchase #7	$196.72	13.173%	$222.6339	$222.63	$222.65	$222.60
7 purchase totals =	$955.55		$1,033.5144	$1,033.52	$1,033.55	$1,033.50