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	$200.36	11.537%	$223.4755	$223.48	$223.50	$223.50
Purchase #2	$200.72	11.435%	$223.6723	$223.67	$223.65	$223.70
Purchase #3	$73.54	7.686%	$79.1923	$79.19	$79.20	$79.20
Purchase #4	$77.68	6.203%	$82.4985	$82.50	$82.50	$82.50
Purchase #5	$29.70	11.293%	$33.054	$33.05	$33.05	$33.10
Purchase #6	$151.90	3.103%	$156.6135	$156.61	$156.60	$156.60
Purchase #7	$168.83	13.520%	$191.6558	$191.66	$191.65	$191.70
7 purchase totals =	$902.73		$990.1619	$990.16	$990.15	$990.30