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	$53.88	7.391%	$57.8623	$57.86	$57.85	$57.90
Purchase #2	$28.43	11.826%	$31.7921	$31.79	$31.80	$31.80
Purchase #3	$137.92	8.604%	$149.7866	$149.79	$149.80	$149.80
Purchase #4	$171.87	4.676%	$179.9066	$179.91	$179.90	$179.90
Purchase #5	$76.58	8.344%	$82.9698	$82.97	$82.95	$83.00
Purchase #6	$149.31	8.650%	$162.2253	$162.23	$162.25	$162.20
Purchase #7	$167.47	3.208%	$172.8424	$172.84	$172.85	$172.80
7 purchase totals =	$785.46		$837.3851	$837.39	$837.40	$837.40