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	$121.65	7.820%	$131.163	$131.16	$131.15	$131.20
Purchase #2	$59.75	7.672%	$64.334	$64.33	$64.35	$64.30
Purchase #3	$33.34	11.690%	$37.2374	$37.24	$37.25	$37.20
Purchase #4	$42.77	6.129%	$45.3914	$45.39	$45.40	$45.40
Purchase #5	$90.90	7.188%	$97.4339	$97.43	$97.45	$97.40
Purchase #6	$194.67	11.360%	$216.7845	$216.78	$216.80	$216.80
Purchase #7	$58.79	9.160%	$64.1752	$64.18	$64.20	$64.20
7 purchase totals =	$601.87		$656.5194	$656.51	$656.60	$656.50