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	$209.47	6.422%	$222.9222	$222.92	$222.90	$222.90
Purchase #2	$9.54	12.196%	$10.7035	$10.70	$10.70	$10.70
Purchase #3	$144.50	4.215%	$150.5907	$150.59	$150.60	$150.60
Purchase #4	$185.53	11.267%	$206.4337	$206.43	$206.45	$206.40
Purchase #5	$152.79	6.755%	$163.111	$163.11	$163.10	$163.10
Purchase #6	$47.86	10.513%	$52.8915	$52.89	$52.90	$52.90
Purchase #7	$82.51	12.419%	$92.7569	$92.76	$92.75	$92.80
7 purchase totals =	$832.20		$899.4095	$899.40	$899.40	$899.40