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	$213.89	12.136%	$239.8477	$239.85	$239.85	$239.80
Purchase #2	$168.80	11.215%	$187.7309	$187.73	$187.75	$187.70
Purchase #3	$84.54	8.512%	$91.736	$91.74	$91.75	$91.70
Purchase #4	$147.89	11.617%	$165.0704	$165.07	$165.05	$165.10
Purchase #5	$90.78	9.390%	$99.3042	$99.30	$99.30	$99.30
Purchase #6	$191.68	13.125%	$216.838	$216.84	$216.85	$216.80
Purchase #7	$99.30	11.248%	$110.4693	$110.47	$110.45	$110.50
7 purchase totals =	$996.88		$1,110.9965	$1,111.00	$1,111.00	$1,110.90