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	$51.38	10.475%	$56.7621	$56.76	$56.75	$56.80
Purchase #2	$159.49	3.874%	$165.6686	$165.67	$165.65	$165.70
Purchase #3	$54.63	10.768%	$60.5126	$60.51	$60.50	$60.50
Purchase #4	$196.39	13.204%	$222.3213	$222.32	$222.30	$222.30
Purchase #5	$214.76	10.220%	$236.7085	$236.71	$236.70	$236.70
Purchase #6	$41.39	3.583%	$42.873	$42.87	$42.85	$42.90
Purchase #7	$136.92	7.716%	$147.4847	$147.48	$147.50	$147.50
7 purchase totals =	$854.96		$932.3308	$932.32	$932.25	$932.40