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	$195.91	7.375%	$210.3584	$210.36	$210.35	$210.40
Purchase #2	$70.94	3.522%	$73.4385	$73.44	$73.45	$73.40
Purchase #3	$117.44	11.630%	$131.0983	$131.10	$131.10	$131.10
Purchase #4	$81.92	9.510%	$89.7106	$89.71	$89.70	$89.70
Purchase #5	$52.90	12.592%	$59.5612	$59.56	$59.55	$59.60
Purchase #6	$41.78	13.468%	$47.4069	$47.41	$47.40	$47.40
Purchase #7	$55.39	13.500%	$62.8677	$62.87	$62.85	$62.90
7 purchase totals =	$616.28		$674.4416	$674.45	$674.40	$674.50