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	$131.95	11.330%	$146.8999	$146.90	$146.90	$146.90
Purchase #2	$102.90	8.693%	$111.8451	$111.85	$111.85	$111.80
Purchase #3	$170.32	8.309%	$184.4719	$184.47	$184.45	$184.50
Purchase #4	$165.53	7.606%	$178.1202	$178.12	$178.10	$178.10
Purchase #5	$200.40	13.600%	$227.6544	$227.65	$227.65	$227.70
Purchase #6	$193.32	4.770%	$202.5414	$202.54	$202.55	$202.50
Purchase #7	$194.31	13.166%	$219.8929	$219.89	$219.90	$219.90
7 purchase totals =	$1,158.73		$1,271.4258	$1,271.42	$1,271.40	$1,271.40