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	$41.31	3.147%	$42.61	$42.61	$42.60	$42.60
Purchase #2	$151.53	3.285%	$156.5078	$156.51	$156.50	$156.50
Purchase #3	$182.34	7.709%	$196.3966	$196.40	$196.40	$196.40
Purchase #4	$198.94	5.452%	$209.7862	$209.79	$209.80	$209.80
Purchase #5	$146.73	12.292%	$164.7661	$164.77	$164.75	$164.80
Purchase #6	$213.95	13.463%	$242.7541	$242.75	$242.75	$242.80
Purchase #7	$200.57	3.111%	$206.8097	$206.81	$206.80	$206.80
7 purchase totals =	$1,135.37		$1,219.6305	$1,219.64	$1,219.60	$1,219.70