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	$40.92	12.726%	$46.1275	$46.13	$46.15	$46.10
Purchase #2	$150.39	9.300%	$164.3763	$164.38	$164.40	$164.40
Purchase #3	$135.89	3.207%	$140.248	$140.25	$140.25	$140.20
Purchase #4	$21.43	3.672%	$22.2169	$22.22	$22.20	$22.20
Purchase #5	$88.85	6.222%	$94.3782	$94.38	$94.40	$94.40
Purchase #6	$140.27	3.204%	$144.7643	$144.76	$144.75	$144.80
Purchase #7	$12.56	12.179%	$14.0897	$14.09	$14.10	$14.10
7 purchase totals =	$590.31		$626.2009	$626.21	$626.25	$626.20