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	$195.88	4.341%	$204.3832	$204.38	$204.40	$204.40
Purchase #2	$245.27	13.532%	$278.4599	$278.46	$278.45	$278.50
Purchase #3	$124.87	12.118%	$140.0017	$140.00	$140.00	$140.00
Purchase #4	$130.89	8.405%	$141.8913	$141.89	$141.90	$141.90
Purchase #5	$148.48	11.864%	$166.0957	$166.10	$166.10	$166.10
Purchase #6	$188.66	3.168%	$194.6367	$194.64	$194.65	$194.60
Purchase #7	$48.86	9.353%	$53.4299	$53.43	$53.45	$53.40
7 purchase totals =	$1,082.91		$1,178.8984	$1,178.90	$1,178.95	$1,178.90