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	$245.95	4.450%	$256.8948	$256.89	$256.90	$256.90
Purchase #2	$232.27	9.810%	$255.0557	$255.06	$255.05	$255.10
Purchase #3	$130.81	7.263%	$140.3107	$140.31	$140.30	$140.30
Purchase #4	$161.29	11.563%	$179.94	$179.94	$179.95	$179.90
Purchase #5	$34.36	13.188%	$38.8914	$38.89	$38.90	$38.90
Purchase #6	$40.70	12.371%	$45.735	$45.74	$45.75	$45.70
Purchase #7	$243.88	3.751%	$253.0279	$253.03	$253.05	$253.00
7 purchase totals =	$1,089.26		$1,169.8555	$1,169.86	$1,169.90	$1,169.80