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	$160.29	10.133%	$176.5322	$176.53	$176.55	$176.50
Purchase #2	$217.79	11.744%	$243.3673	$243.37	$243.35	$243.40
Purchase #3	$167.27	13.793%	$190.3416	$190.34	$190.35	$190.30
Purchase #4	$216.54	11.680%	$241.8319	$241.83	$241.85	$241.80
Purchase #5	$244.74	8.643%	$265.8929	$265.89	$265.90	$265.90
Purchase #6	$78.52	6.156%	$83.3537	$83.35	$83.35	$83.40
Purchase #7	$171.81	10.184%	$189.3071	$189.31	$189.30	$189.30
7 purchase totals =	$1,256.96		$1,390.6267	$1,390.62	$1,390.65	$1,390.60