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	$54.33	4.739%	$56.9047	$56.90	$56.90	$56.90
Purchase #2	$22.78	11.803%	$25.4687	$25.47	$25.45	$25.50
Purchase #3	$36.83	9.792%	$40.4364	$40.44	$40.45	$40.40
Purchase #4	$236.90	9.469%	$259.3321	$259.33	$259.35	$259.30
Purchase #5	$244.49	8.711%	$265.7875	$265.79	$265.80	$265.80
Purchase #6	$11.72	5.642%	$12.3812	$12.38	$12.40	$12.40
Purchase #7	$32.79	7.105%	$35.1197	$35.12	$35.10	$35.10
7 purchase totals =	$639.84		$695.4303	$695.43	$695.45	$695.40