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	$77.50	7.466%	$83.2862	$83.29	$83.30	$83.30
Purchase #2	$66.61	11.667%	$74.3814	$74.38	$74.40	$74.40
Purchase #3	$82.66	11.325%	$92.0212	$92.02	$92.00	$92.00
Purchase #4	$237.25	5.862%	$251.1576	$251.16	$251.15	$251.20
Purchase #5	$198.25	3.351%	$204.8934	$204.89	$204.90	$204.90
Purchase #6	$157.46	6.188%	$167.2036	$167.20	$167.20	$167.20
Purchase #7	$202.64	9.780%	$222.4582	$222.46	$222.45	$222.50
7 purchase totals =	$1,022.37		$1,095.4016	$1,095.40	$1,095.40	$1,095.50