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	$117.67	4.772%	$123.2852	$123.29	$123.30	$123.30
Purchase #2	$85.38	5.138%	$89.7668	$89.77	$89.75	$89.80
Purchase #3	$42.47	13.561%	$48.2294	$48.23	$48.25	$48.20
Purchase #4	$161.86	12.206%	$181.6166	$181.62	$181.60	$181.60
Purchase #5	$54.37	6.228%	$57.7562	$57.76	$57.75	$57.80
Purchase #6	$227.59	11.431%	$253.6058	$253.61	$253.60	$253.60
Purchase #7	$101.79	6.426%	$108.331	$108.33	$108.35	$108.30
7 purchase totals =	$791.13		$862.5910	$862.61	$862.60	$862.60