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	$68.48	10.321%	$75.5478	$75.55	$75.55	$75.50
Purchase #2	$19.91	13.242%	$22.5465	$22.55	$22.55	$22.50
Purchase #3	$187.52	12.727%	$211.3857	$211.39	$211.40	$211.40
Purchase #4	$237.55	11.143%	$264.0202	$264.02	$264.00	$264.00
Purchase #5	$68.58	11.579%	$76.5209	$76.52	$76.50	$76.50
Purchase #6	$57.91	5.568%	$61.1344	$61.13	$61.15	$61.10
Purchase #7	$69.32	12.832%	$78.2151	$78.22	$78.20	$78.20
7 purchase totals =	$709.27		$789.3706	$789.38	$789.35	$789.20