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	$129.98	10.597%	$143.754	$143.75	$143.75	$143.80
Purchase #2	$134.49	12.325%	$151.0659	$151.07	$151.05	$151.10
Purchase #3	$81.80	5.753%	$86.506	$86.51	$86.50	$86.50
Purchase #4	$94.79	6.222%	$100.6878	$100.69	$100.70	$100.70
Purchase #5	$86.76	4.774%	$90.9019	$90.90	$90.90	$90.90
Purchase #6	$187.25	4.538%	$195.7474	$195.75	$195.75	$195.70
Purchase #7	$136.95	8.346%	$148.3798	$148.38	$148.40	$148.40
7 purchase totals =	$852.02		$917.0428	$917.05	$917.05	$917.10