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	$94.43	4.555%	$98.7313	$98.73	$98.75	$98.70
Purchase #2	$6.39	13.847%	$7.2748	$7.27	$7.25	$7.30
Purchase #3	$32.25	11.331%	$35.9042	$35.90	$35.90	$35.90
Purchase #4	$100.77	12.819%	$113.6877	$113.69	$113.70	$113.70
Purchase #5	$159.85	5.398%	$168.4787	$168.48	$168.50	$168.50
Purchase #6	$196.93	4.613%	$206.0144	$206.01	$206.00	$206.00
Purchase #7	$143.71	3.344%	$148.5157	$148.52	$148.50	$148.50
7 purchase totals =	$734.33		$778.6068	$778.60	$778.60	$778.60