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	$145.66	12.526%	$163.9054	$163.91	$163.90	$163.90
Purchase #2	$231.43	11.865%	$258.8892	$258.89	$258.90	$258.90
Purchase #3	$189.43	13.792%	$215.5562	$215.56	$215.55	$215.60
Purchase #4	$20.91	3.768%	$21.6979	$21.70	$21.70	$21.70
Purchase #5	$143.70	5.117%	$151.0531	$151.05	$151.05	$151.10
Purchase #6	$147.31	7.539%	$158.4157	$158.42	$158.40	$158.40
Purchase #7	$69.69	12.678%	$78.5253	$78.53	$78.55	$78.50
7 purchase totals =	$948.13		$1,048.0428	$1,048.06	$1,048.05	$1,048.10