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	$199.56	6.684%	$212.8986	$212.90	$212.90	$212.90
Purchase #2	$171.84	11.450%	$191.5157	$191.52	$191.50	$191.50
Purchase #3	$43.95	12.850%	$49.5976	$49.60	$49.60	$49.60
Purchase #4	$13.59	8.405%	$14.7322	$14.73	$14.75	$14.70
Purchase #5	$228.51	10.753%	$253.0817	$253.08	$253.10	$253.10
Purchase #6	$58.53	5.245%	$61.5999	$61.60	$61.60	$61.60
Purchase #7	$219.61	3.464%	$227.2173	$227.22	$227.20	$227.20
7 purchase totals =	$935.59		$1,010.6430	$1,010.65	$1,010.65	$1,010.60