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	$102.36	8.591%	$111.1537	$111.15	$111.15	$111.20
Purchase #2	$99.31	12.386%	$111.6105	$111.61	$111.60	$111.60
Purchase #3	$136.78	10.193%	$150.722	$150.72	$150.70	$150.70
Purchase #4	$91.90	7.253%	$98.5655	$98.57	$98.55	$98.60
Purchase #5	$31.40	8.168%	$33.9648	$33.96	$33.95	$34.00
Purchase #6	$133.25	5.441%	$140.5001	$140.50	$140.50	$140.50
Purchase #7	$96.66	9.129%	$105.4841	$105.48	$105.50	$105.50
7 purchase totals =	$691.66		$752.0007	$751.99	$751.95	$752.10