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	$143.69	5.193%	$151.1518	$151.15	$151.15	$151.20
Purchase #2	$42.75	6.346%	$45.4629	$45.46	$45.45	$45.50
Purchase #3	$91.95	10.513%	$101.6167	$101.62	$101.60	$101.60
Purchase #4	$40.65	11.829%	$45.4585	$45.46	$45.45	$45.50
Purchase #5	$27.68	3.183%	$28.5611	$28.56	$28.55	$28.60
Purchase #6	$216.67	12.580%	$243.9271	$243.93	$243.95	$243.90
Purchase #7	$190.50	8.185%	$206.0924	$206.09	$206.10	$206.10
7 purchase totals =	$753.89		$822.2705	$822.27	$822.25	$822.40