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	$132.84	11.116%	$147.6065	$147.61	$147.60	$147.60
Purchase #2	$157.96	11.363%	$175.909	$175.91	$175.90	$175.90
Purchase #3	$96.94	8.321%	$105.0064	$105.01	$105.00	$105.00
Purchase #4	$169.78	13.629%	$192.9193	$192.92	$192.90	$192.90
Purchase #5	$30.28	8.757%	$32.9316	$32.93	$32.95	$32.90
Purchase #6	$170.89	6.417%	$181.856	$181.86	$181.85	$181.90
Purchase #7	$176.51	3.530%	$182.7408	$182.74	$182.75	$182.70
7 purchase totals =	$935.20		$1,018.9696	$1,018.98	$1,018.95	$1,018.90