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	$229.78	11.675%	$256.6068	$256.61	$256.60	$256.60
Purchase #2	$135.39	8.874%	$147.4045	$147.40	$147.40	$147.40
Purchase #3	$38.65	13.559%	$43.8906	$43.89	$43.90	$43.90
Purchase #4	$155.84	9.803%	$171.117	$171.12	$171.10	$171.10
Purchase #5	$38.37	10.738%	$42.4902	$42.49	$42.50	$42.50
Purchase #6	$18.36	13.289%	$20.7999	$20.80	$20.80	$20.80
Purchase #7	$42.46	5.349%	$44.7312	$44.73	$44.75	$44.70
7 purchase totals =	$658.85		$727.0402	$727.04	$727.05	$727.00