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	$61.42	9.448%	$67.223	$67.22	$67.20	$67.20
Purchase #2	$65.49	3.212%	$67.5935	$67.59	$67.60	$67.60
Purchase #3	$27.80	4.488%	$29.0477	$29.05	$29.05	$29.00
Purchase #4	$188.78	11.126%	$209.7837	$209.78	$209.80	$209.80
Purchase #5	$168.84	12.261%	$189.5415	$189.54	$189.55	$189.50
Purchase #6	$39.34	13.408%	$44.6147	$44.61	$44.60	$44.60
Purchase #7	$92.40	11.132%	$102.686	$102.69	$102.70	$102.70
7 purchase totals =	$644.07		$710.4901	$710.48	$710.50	$710.40