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	$86.91	11.535%	$96.9351	$96.94	$96.95	$96.90
Purchase #2	$250.33	5.594%	$264.3335	$264.33	$264.35	$264.30
Purchase #3	$157.85	4.191%	$164.4655	$164.47	$164.45	$164.50
Purchase #4	$188.58	4.185%	$196.4721	$196.47	$196.45	$196.50
Purchase #5	$131.66	5.185%	$138.4866	$138.49	$138.50	$138.50
Purchase #6	$199.95	3.510%	$206.9682	$206.97	$206.95	$207.00
Purchase #7	$47.51	3.468%	$49.1576	$49.16	$49.15	$49.20
7 purchase totals =	$1,062.79		$1,116.8186	$1,116.83	$1,116.80	$1,116.90