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	$61.54	9.137%	$67.1629	$67.16	$67.15	$67.20
Purchase #2	$170.41	8.365%	$184.6648	$184.66	$184.65	$184.70
Purchase #3	$92.25	13.677%	$104.867	$104.87	$104.85	$104.90
Purchase #4	$26.46	8.166%	$28.6207	$28.62	$28.60	$28.60
Purchase #5	$43.63	4.465%	$45.5781	$45.58	$45.60	$45.60
Purchase #6	$162.62	3.870%	$168.9134	$168.91	$168.90	$168.90
Purchase #7	$15.87	10.515%	$17.5387	$17.54	$17.55	$17.50
7 purchase totals =	$572.78		$617.3456	$617.34	$617.30	$617.40