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	$176.84	11.243%	$196.7221	$196.72	$196.70	$196.70
Purchase #2	$125.87	4.249%	$131.2182	$131.22	$131.20	$131.20
Purchase #3	$73.61	6.367%	$78.2967	$78.30	$78.30	$78.30
Purchase #4	$243.46	11.777%	$272.1323	$272.13	$272.15	$272.10
Purchase #5	$162.36	6.464%	$172.855	$172.86	$172.85	$172.90
Purchase #6	$32.36	7.571%	$34.81	$34.81	$34.80	$34.80
Purchase #7	$27.64	4.369%	$28.8476	$28.85	$28.85	$28.80
7 purchase totals =	$842.14		$914.8819	$914.89	$914.85	$914.80