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	$147.93	11.362%	$164.7378	$164.74	$164.75	$164.70
Purchase #2	$156.85	9.862%	$172.3185	$172.32	$172.30	$172.30
Purchase #3	$216.43	5.377%	$228.0674	$228.07	$228.05	$228.10
Purchase #4	$196.45	7.780%	$211.7338	$211.73	$211.75	$211.70
Purchase #5	$99.37	4.547%	$103.8884	$103.89	$103.90	$103.90
Purchase #6	$201.34	3.519%	$208.4252	$208.43	$208.45	$208.40
Purchase #7	$100.90	3.556%	$104.488	$104.49	$104.50	$104.50
7 purchase totals =	$1,119.27		$1,193.6591	$1,193.67	$1,193.70	$1,193.60