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	$206.46	9.279%	$225.6174	$225.62	$225.60	$225.60
Purchase #2	$52.67	10.675%	$58.2925	$58.29	$58.30	$58.30
Purchase #3	$155.44	8.454%	$168.5809	$168.58	$168.60	$168.60
Purchase #4	$243.26	13.689%	$276.5599	$276.56	$276.55	$276.60
Purchase #5	$43.54	4.857%	$45.6547	$45.65	$45.65	$45.70
Purchase #6	$220.77	8.163%	$238.7915	$238.79	$238.80	$238.80
Purchase #7	$183.47	13.797%	$208.7834	$208.78	$208.80	$208.80
7 purchase totals =	$1,105.61		$1,222.2803	$1,222.27	$1,222.30	$1,222.40