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	$30.73	7.487%	$33.0308	$33.03	$33.05	$33.00
Purchase #2	$66.31	11.206%	$73.7407	$73.74	$73.75	$73.70
Purchase #3	$100.31	9.256%	$109.5947	$109.59	$109.60	$109.60
Purchase #4	$120.64	3.256%	$124.568	$124.57	$124.55	$124.60
Purchase #5	$20.86	12.148%	$23.3941	$23.39	$23.40	$23.40
Purchase #6	$25.42	9.725%	$27.8921	$27.89	$27.90	$27.90
Purchase #7	$29.96	11.158%	$33.3029	$33.30	$33.30	$33.30
7 purchase totals =	$394.23		$425.5233	$425.51	$425.55	$425.50