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	$82.40	11.668%	$92.0144	$92.01	$92.00	$92.00
Purchase #2	$36.55	3.815%	$37.9444	$37.94	$37.95	$37.90
Purchase #3	$165.85	4.214%	$172.8389	$172.84	$172.85	$172.80
Purchase #4	$88.90	8.563%	$96.5125	$96.51	$96.50	$96.50
Purchase #5	$201.43	12.700%	$227.0116	$227.01	$227.00	$227.00
Purchase #6	$222.69	6.518%	$237.2049	$237.20	$237.20	$237.20
Purchase #7	$133.34	3.409%	$137.8856	$137.89	$137.90	$137.90
7 purchase totals =	$931.16		$1,001.4123	$1,001.40	$1,001.40	$1,001.30