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	$69.85	3.406%	$72.2291	$72.23	$72.25	$72.20
Purchase #2	$216.68	4.228%	$225.8412	$225.84	$225.85	$225.80
Purchase #3	$14.41	12.502%	$16.2115	$16.21	$16.20	$16.20
Purchase #4	$156.52	9.226%	$170.9605	$170.96	$170.95	$171.00
Purchase #5	$184.74	8.349%	$200.1639	$200.16	$200.15	$200.20
Purchase #6	$217.43	9.846%	$238.8382	$238.84	$238.85	$238.80
Purchase #7	$72.25	8.578%	$78.4476	$78.45	$78.45	$78.40
7 purchase totals =	$931.88		$1,002.6920	$1,002.69	$1,002.70	$1,002.60