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	$59.63	5.210%	$62.7367	$62.74	$62.75	$62.70
Purchase #2	$145.41	5.112%	$152.8434	$152.84	$152.85	$152.80
Purchase #3	$45.82	4.494%	$47.8792	$47.88	$47.90	$47.90
Purchase #4	$86.71	7.828%	$93.4977	$93.50	$93.50	$93.50
Purchase #5	$190.43	4.115%	$198.2662	$198.27	$198.25	$198.30
Purchase #6	$89.56	12.165%	$100.455	$100.46	$100.45	$100.50
Purchase #7	$13.58	12.362%	$15.2588	$15.26	$15.25	$15.30
7 purchase totals =	$631.14		$670.9370	$670.95	$670.95	$671.00