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	$32.97	6.515%	$35.118	$35.12	$35.10	$35.10
Purchase #2	$59.72	3.216%	$61.6406	$61.64	$61.65	$61.60
Purchase #3	$10.28	13.761%	$11.6946	$11.69	$11.70	$11.70
Purchase #4	$84.56	3.563%	$87.5729	$87.57	$87.55	$87.60
Purchase #5	$94.38	5.656%	$99.7181	$99.72	$99.70	$99.70
Purchase #6	$58.93	5.285%	$62.0445	$62.04	$62.05	$62.00
Purchase #7	$108.36	10.242%	$119.4582	$119.46	$119.45	$119.50
7 purchase totals =	$449.20		$477.2469	$477.24	$477.20	$477.20