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	$177.34	6.808%	$189.4133	$189.41	$189.40	$189.40
Purchase #2	$12.92	4.203%	$13.463	$13.46	$13.45	$13.50
Purchase #3	$76.62	8.758%	$83.3304	$83.33	$83.35	$83.30
Purchase #4	$234.78	8.359%	$254.4053	$254.41	$254.40	$254.40
Purchase #5	$236.53	7.624%	$254.563	$254.56	$254.55	$254.60
Purchase #6	$245.82	12.161%	$275.7142	$275.71	$275.70	$275.70
Purchase #7	$54.56	8.812%	$59.3678	$59.37	$59.35	$59.40
7 purchase totals =	$1,038.57		$1,130.2570	$1,130.25	$1,130.20	$1,130.30