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	$60.77	11.479%	$67.7458	$67.75	$67.75	$67.70
Purchase #2	$86.37	5.504%	$91.1238	$91.12	$91.10	$91.10
Purchase #3	$134.51	3.767%	$139.577	$139.58	$139.60	$139.60
Purchase #4	$124.92	4.768%	$130.8762	$130.88	$130.90	$130.90
Purchase #5	$49.83	11.418%	$55.5196	$55.52	$55.50	$55.50
Purchase #6	$234.30	11.464%	$261.1602	$261.16	$261.15	$261.20
Purchase #7	$125.36	12.773%	$141.3722	$141.37	$141.35	$141.40
7 purchase totals =	$816.06		$887.3748	$887.38	$887.35	$887.40