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	$141.61	12.749%	$159.6639	$159.66	$159.65	$159.70
Purchase #2	$150.69	10.653%	$166.743	$166.74	$166.75	$166.70
Purchase #3	$55.66	11.310%	$61.9551	$61.96	$61.95	$62.00
Purchase #4	$98.29	12.172%	$110.2539	$110.25	$110.25	$110.30
Purchase #5	$129.73	10.155%	$142.9041	$142.90	$142.90	$142.90
Purchase #6	$104.34	5.168%	$109.7323	$109.73	$109.75	$109.70
Purchase #7	$92.51	3.617%	$95.8561	$95.86	$95.85	$95.90
7 purchase totals =	$772.83		$847.1084	$847.10	$847.10	$847.20