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	$23.69	6.643%	$25.2637	$25.26	$25.25	$25.30
Purchase #2	$236.57	8.420%	$256.4892	$256.49	$256.50	$256.50
Purchase #3	$156.64	3.683%	$162.4091	$162.41	$162.40	$162.40
Purchase #4	$122.82	4.592%	$128.4599	$128.46	$128.45	$128.50
Purchase #5	$94.53	11.167%	$105.0862	$105.09	$105.10	$105.10
Purchase #6	$132.86	9.834%	$145.9255	$145.93	$145.95	$145.90
Purchase #7	$227.58	11.460%	$253.6607	$253.66	$253.65	$253.70
7 purchase totals =	$994.69		$1,077.2943	$1,077.30	$1,077.30	$1,077.40