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	$112.25	12.709%	$126.5159	$126.52	$126.50	$126.50
Purchase #2	$111.59	3.276%	$115.2457	$115.25	$115.25	$115.20
Purchase #3	$99.62	9.824%	$109.4067	$109.41	$109.40	$109.40
Purchase #4	$38.67	5.261%	$40.7044	$40.70	$40.70	$40.70
Purchase #5	$71.72	11.689%	$80.1034	$80.10	$80.10	$80.10
Purchase #6	$67.72	12.685%	$76.3103	$76.31	$76.30	$76.30
Purchase #7	$27.84	6.485%	$29.6454	$29.65	$29.65	$29.60
7 purchase totals =	$529.41		$577.9318	$577.94	$577.90	$577.80