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	$181.46	10.497%	$200.5079	$200.51	$200.50	$200.50
Purchase #2	$57.73	11.858%	$64.5756	$64.58	$64.60	$64.60
Purchase #3	$196.56	8.497%	$213.2617	$213.26	$213.25	$213.30
Purchase #4	$5.91	10.121%	$6.5082	$6.51	$6.50	$6.50
Purchase #5	$7.64	3.698%	$7.9225	$7.92	$7.90	$7.90
Purchase #6	$147.52	5.275%	$155.3017	$155.30	$155.30	$155.30
Purchase #7	$107.67	3.589%	$111.5343	$111.53	$111.55	$111.50
7 purchase totals =	$704.49		$759.6119	$759.61	$759.60	$759.60