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	$73.27	12.297%	$82.28	$82.28	$82.30	$82.30
Purchase #2	$57.39	9.105%	$62.6154	$62.62	$62.60	$62.60
Purchase #3	$57.29	7.616%	$61.6532	$61.65	$61.65	$61.70
Purchase #4	$91.34	3.388%	$94.4346	$94.43	$94.45	$94.40
Purchase #5	$120.54	9.279%	$131.7249	$131.72	$131.70	$131.70
Purchase #6	$5.36	12.297%	$6.0191	$6.02	$6.00	$6.00
Purchase #7	$178.51	10.337%	$196.9626	$196.96	$196.95	$197.00
7 purchase totals =	$583.70		$635.6898	$635.68	$635.65	$635.70