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	$71.81	6.694%	$76.617	$76.62	$76.60	$76.60
Purchase #2	$110.72	5.439%	$116.7421	$116.74	$116.75	$116.70
Purchase #3	$6.87	11.602%	$7.6671	$7.67	$7.65	$7.70
Purchase #4	$155.41	5.613%	$164.1332	$164.13	$164.15	$164.10
Purchase #5	$58.98	12.465%	$66.3319	$66.33	$66.35	$66.30
Purchase #6	$90.84	13.650%	$103.2397	$103.24	$103.25	$103.20
Purchase #7	$171.84	4.260%	$179.1604	$179.16	$179.15	$179.20
7 purchase totals =	$666.47		$713.8914	$713.89	$713.90	$713.80