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	$80.82	9.735%	$88.6878	$88.69	$88.70	$88.70
Purchase #2	$92.59	8.495%	$100.4555	$100.46	$100.45	$100.50
Purchase #3	$149.82	10.727%	$165.8912	$165.89	$165.90	$165.90
Purchase #4	$43.88	5.770%	$46.4119	$46.41	$46.40	$46.40
Purchase #5	$54.95	7.725%	$59.1949	$59.19	$59.20	$59.20
Purchase #6	$95.28	10.601%	$105.3806	$105.38	$105.40	$105.40
Purchase #7	$159.39	6.150%	$169.1925	$169.19	$169.20	$169.20
7 purchase totals =	$676.73		$735.2144	$735.21	$735.25	$735.30