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	$173.54	6.805%	$185.3494	$185.35	$185.35	$185.30
Purchase #2	$166.78	13.507%	$189.307	$189.31	$189.30	$189.30
Purchase #3	$131.87	10.320%	$145.479	$145.48	$145.50	$145.50
Purchase #4	$152.25	11.539%	$169.8181	$169.82	$169.80	$169.80
Purchase #5	$25.81	5.828%	$27.3142	$27.31	$27.30	$27.30
Purchase #6	$104.44	11.573%	$116.5268	$116.53	$116.55	$116.50
Purchase #7	$33.74	10.760%	$37.3704	$37.37	$37.35	$37.40
7 purchase totals =	$788.43		$871.1649	$871.17	$871.15	$871.10