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	$30.29	8.132%	$32.7532	$32.75	$32.75	$32.80
Purchase #2	$225.86	3.454%	$233.6612	$233.66	$233.65	$233.70
Purchase #3	$78.73	6.280%	$83.6742	$83.67	$83.65	$83.70
Purchase #4	$161.29	7.579%	$173.5142	$173.51	$173.50	$173.50
Purchase #5	$109.90	8.524%	$119.2679	$119.27	$119.25	$119.30
Purchase #6	$136.25	11.641%	$152.1109	$152.11	$152.10	$152.10
Purchase #7	$204.27	4.853%	$214.1832	$214.18	$214.20	$214.20
7 purchase totals =	$946.59		$1,009.1648	$1,009.15	$1,009.10	$1,009.30