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	$54.66	8.226%	$59.1563	$59.16	$59.15	$59.20
Purchase #2	$160.91	8.145%	$174.0161	$174.02	$174.00	$174.00
Purchase #3	$203.43	9.556%	$222.8698	$222.87	$222.85	$222.90
Purchase #4	$99.40	10.778%	$110.1133	$110.11	$110.10	$110.10
Purchase #5	$41.28	11.141%	$45.879	$45.88	$45.90	$45.90
Purchase #6	$179.30	11.361%	$199.6703	$199.67	$199.65	$199.70
Purchase #7	$76.37	5.811%	$80.8079	$80.81	$80.80	$80.80
7 purchase totals =	$815.35		$892.5127	$892.52	$892.45	$892.60