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	$227.34	11.557%	$253.6137	$253.61	$253.60	$253.60
Purchase #2	$152.84	8.345%	$165.5945	$165.59	$165.60	$165.60
Purchase #3	$102.60	5.580%	$108.3251	$108.33	$108.35	$108.30
Purchase #4	$42.69	12.741%	$48.1291	$48.13	$48.15	$48.10
Purchase #5	$168.55	13.453%	$191.225	$191.23	$191.25	$191.20
Purchase #6	$80.34	13.618%	$91.2807	$91.28	$91.30	$91.30
Purchase #7	$219.28	9.822%	$240.8177	$240.82	$240.80	$240.80
7 purchase totals =	$993.64		$1,098.9858	$1,098.99	$1,099.05	$1,098.90