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	$197.72	12.371%	$222.1799	$222.18	$222.20	$222.20
Purchase #2	$234.72	12.105%	$263.1329	$263.13	$263.15	$263.10
Purchase #3	$116.86	4.228%	$121.8008	$121.80	$121.80	$121.80
Purchase #4	$71.57	13.774%	$81.4281	$81.43	$81.45	$81.40
Purchase #5	$48.52	13.135%	$54.8931	$54.89	$54.90	$54.90
Purchase #6	$209.88	11.839%	$234.7277	$234.73	$234.75	$234.70
Purchase #7	$141.34	10.642%	$156.3814	$156.38	$156.40	$156.40
7 purchase totals =	$1,020.61		$1,134.5439	$1,134.54	$1,134.65	$1,134.50