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	$235.77	7.417%	$253.2571	$253.26	$253.25	$253.30
Purchase #2	$54.26	10.559%	$59.9893	$59.99	$60.00	$60.00
Purchase #3	$7.67	9.171%	$8.3734	$8.37	$8.35	$8.40
Purchase #4	$66.85	13.741%	$76.0359	$76.04	$76.05	$76.00
Purchase #5	$233.89	9.380%	$255.8289	$255.83	$255.85	$255.80
Purchase #6	$244.27	4.844%	$256.1024	$256.10	$256.10	$256.10
Purchase #7	$159.64	5.743%	$168.8081	$168.81	$168.80	$168.80
7 purchase totals =	$1,002.35		$1,078.3951	$1,078.40	$1,078.40	$1,078.40