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	$59.57	12.733%	$67.155	$67.16	$67.15	$67.20
Purchase #2	$87.82	9.311%	$95.9969	$96.00	$96.00	$96.00
Purchase #3	$58.68	8.616%	$63.7359	$63.74	$63.75	$63.70
Purchase #4	$104.63	5.516%	$110.4014	$110.40	$110.40	$110.40
Purchase #5	$123.82	12.736%	$139.5897	$139.59	$139.60	$139.60
Purchase #6	$57.47	7.692%	$61.8906	$61.89	$61.90	$61.90
Purchase #7	$20.47	4.722%	$21.4366	$21.44	$21.45	$21.40
7 purchase totals =	$512.46		$560.2061	$560.22	$560.25	$560.20