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	$95.63	4.474%	$99.9085	$99.91	$99.90	$99.90
Purchase #2	$227.89	12.447%	$256.2555	$256.26	$256.25	$256.30
Purchase #3	$160.89	6.620%	$171.5409	$171.54	$171.55	$171.50
Purchase #4	$144.70	4.625%	$151.3924	$151.39	$151.40	$151.40
Purchase #5	$218.73	3.739%	$226.9083	$226.91	$226.90	$226.90
Purchase #6	$48.75	13.496%	$55.3293	$55.33	$55.35	$55.30
Purchase #7	$51.29	9.843%	$56.3385	$56.34	$56.35	$56.30
7 purchase totals =	$947.88		$1,017.6734	$1,017.68	$1,017.70	$1,017.60