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	$166.53	13.638%	$189.2414	$189.24	$189.25	$189.20
Purchase #2	$91.72	13.638%	$104.2288	$104.23	$104.25	$104.20
Purchase #3	$48.81	9.212%	$53.3064	$53.31	$53.30	$53.30
Purchase #4	$195.89	10.406%	$216.2743	$216.27	$216.25	$216.30
Purchase #5	$222.74	9.750%	$244.4572	$244.46	$244.45	$244.50
Purchase #6	$53.37	12.152%	$59.8555	$59.86	$59.85	$59.90
Purchase #7	$198.29	8.614%	$215.3707	$215.37	$215.35	$215.40
7 purchase totals =	$977.35		$1,082.7343	$1,082.74	$1,082.70	$1,082.80