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	$182.82	7.200%	$195.983	$195.98	$196.00	$196.00
Purchase #2	$233.62	12.625%	$263.1145	$263.11	$263.10	$263.10
Purchase #3	$247.25	7.652%	$266.1696	$266.17	$266.15	$266.20
Purchase #4	$56.98	4.204%	$59.3754	$59.38	$59.40	$59.40
Purchase #5	$91.64	12.456%	$103.0547	$103.05	$103.05	$103.10
Purchase #6	$37.66	13.690%	$42.8157	$42.82	$42.80	$42.80
Purchase #7	$193.93	8.203%	$209.8381	$209.84	$209.85	$209.80
7 purchase totals =	$1,043.90		$1,140.3510	$1,140.35	$1,140.35	$1,140.40