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	$95.32	6.321%	$101.3452	$101.35	$101.35	$101.30
Purchase #2	$40.41	10.548%	$44.6724	$44.67	$44.65	$44.70
Purchase #3	$238.84	10.653%	$264.2836	$264.28	$264.30	$264.30
Purchase #4	$53.65	11.105%	$59.6078	$59.61	$59.60	$59.60
Purchase #5	$39.46	4.662%	$41.2996	$41.30	$41.30	$41.30
Purchase #6	$144.40	4.329%	$150.6511	$150.65	$150.65	$150.70
Purchase #7	$237.63	11.747%	$265.5444	$265.54	$265.55	$265.50
7 purchase totals =	$849.71		$927.4041	$927.40	$927.40	$927.40