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	$192.72	3.534%	$199.5307	$199.53	$199.55	$199.50
Purchase #2	$78.66	9.133%	$85.844	$85.84	$85.85	$85.80
Purchase #3	$105.61	7.862%	$113.9131	$113.91	$113.90	$113.90
Purchase #4	$31.41	4.238%	$32.7412	$32.74	$32.75	$32.70
Purchase #5	$114.95	3.443%	$118.9077	$118.91	$118.90	$118.90
Purchase #6	$204.74	7.676%	$220.4558	$220.46	$220.45	$220.50
Purchase #7	$105.52	6.635%	$112.5213	$112.52	$112.50	$112.50
7 purchase totals =	$833.61		$883.9138	$883.91	$883.90	$883.80