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	$85.80	9.703%	$94.1252	$94.13	$94.15	$94.10
Purchase #2	$47.46	5.470%	$50.0561	$50.06	$50.05	$50.10
Purchase #3	$222.67	3.198%	$229.791	$229.79	$229.80	$229.80
Purchase #4	$51.25	4.776%	$53.6977	$53.70	$53.70	$53.70
Purchase #5	$83.92	12.610%	$94.5023	$94.50	$94.50	$94.50
Purchase #6	$214.56	11.340%	$238.8911	$238.89	$238.90	$238.90
Purchase #7	$6.80	9.154%	$7.4225	$7.42	$7.40	$7.40
7 purchase totals =	$712.46		$768.4859	$768.49	$768.50	$768.50