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	$186.38	6.238%	$198.0064	$198.01	$198.00	$198.00
Purchase #2	$131.35	13.697%	$149.341	$149.34	$149.35	$149.30
Purchase #3	$247.55	3.633%	$256.5435	$256.54	$256.55	$256.50
Purchase #4	$34.46	3.847%	$35.7857	$35.79	$35.80	$35.80
Purchase #5	$180.78	13.334%	$204.8852	$204.89	$204.90	$204.90
Purchase #6	$145.50	3.482%	$150.5663	$150.57	$150.55	$150.60
Purchase #7	$31.80	3.241%	$32.8306	$32.83	$32.85	$32.80
7 purchase totals =	$957.82		$1,027.9587	$1,027.97	$1,028.00	$1,027.90