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	$70.31	11.447%	$78.3584	$78.36	$78.35	$78.40
Purchase #2	$41.94	13.326%	$47.5289	$47.53	$47.55	$47.50
Purchase #3	$209.53	5.675%	$221.4208	$221.42	$221.40	$221.40
Purchase #4	$219.30	11.363%	$244.2191	$244.22	$244.20	$244.20
Purchase #5	$180.41	11.291%	$200.7801	$200.78	$200.80	$200.80
Purchase #6	$103.77	10.626%	$114.7966	$114.80	$114.80	$114.80
Purchase #7	$206.79	4.785%	$216.6849	$216.68	$216.70	$216.70
7 purchase totals =	$1,032.05		$1,123.7888	$1,123.79	$1,123.80	$1,123.80