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	$228.36	8.125%	$246.9143	$246.91	$246.90	$246.90
Purchase #2	$240.59	9.189%	$262.6978	$262.70	$262.70	$262.70
Purchase #3	$213.71	8.353%	$231.5612	$231.56	$231.55	$231.60
Purchase #4	$51.95	13.832%	$59.1357	$59.14	$59.15	$59.10
Purchase #5	$80.81	13.621%	$91.8171	$91.82	$91.80	$91.80
Purchase #6	$149.47	11.367%	$166.4603	$166.46	$166.45	$166.50
Purchase #7	$46.56	13.581%	$52.8833	$52.88	$52.90	$52.90
7 purchase totals =	$1,011.45		$1,111.4697	$1,111.47	$1,111.45	$1,111.50