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	$39.39	13.569%	$44.7348	$44.73	$44.75	$44.70
Purchase #2	$232.65	4.814%	$243.8498	$243.85	$243.85	$243.80
Purchase #3	$16.39	11.812%	$18.326	$18.33	$18.35	$18.30
Purchase #4	$130.89	7.313%	$140.462	$140.46	$140.45	$140.50
Purchase #5	$101.81	6.326%	$108.2505	$108.25	$108.25	$108.30
Purchase #6	$140.91	9.507%	$154.3063	$154.31	$154.30	$154.30
Purchase #7	$100.52	4.385%	$104.9278	$104.93	$104.95	$104.90
7 purchase totals =	$762.56		$814.8572	$814.86	$814.90	$814.80