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	$134.29	7.213%	$143.9763	$143.98	$144.00	$144.00
Purchase #2	$45.89	6.331%	$48.7953	$48.80	$48.80	$48.80
Purchase #3	$152.65	8.646%	$165.8481	$165.85	$165.85	$165.80
Purchase #4	$209.77	9.301%	$229.2807	$229.28	$229.30	$229.30
Purchase #5	$218.97	10.435%	$241.8195	$241.82	$241.80	$241.80
Purchase #6	$178.82	12.248%	$200.7219	$200.72	$200.70	$200.70
Purchase #7	$49.34	4.443%	$51.5322	$51.53	$51.55	$51.50
7 purchase totals =	$989.73		$1,081.9740	$1,081.98	$1,082.00	$1,081.90