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	$91.42	3.280%	$94.4186	$94.42	$94.40	$94.40
Purchase #2	$97.30	12.305%	$109.2728	$109.27	$109.25	$109.30
Purchase #3	$136.29	11.671%	$152.1964	$152.20	$152.20	$152.20
Purchase #4	$236.59	10.760%	$262.0471	$262.05	$262.05	$262.00
Purchase #5	$153.52	3.287%	$158.5662	$158.57	$158.55	$158.60
Purchase #6	$154.39	11.369%	$171.9426	$171.94	$171.95	$171.90
Purchase #7	$21.89	7.117%	$23.4479	$23.45	$23.45	$23.40
7 purchase totals =	$891.40		$971.8916	$971.90	$971.85	$971.80