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	$196.36	6.375%	$208.878	$208.88	$208.90	$208.90
Purchase #2	$83.87	12.796%	$94.602	$94.60	$94.60	$94.60
Purchase #3	$190.89	3.785%	$198.1152	$198.12	$198.10	$198.10
Purchase #4	$57.49	12.231%	$64.5216	$64.52	$64.50	$64.50
Purchase #5	$222.51	8.798%	$242.0864	$242.09	$242.10	$242.10
Purchase #6	$222.46	9.351%	$243.2622	$243.26	$243.25	$243.30
Purchase #7	$148.50	13.449%	$168.4718	$168.47	$168.45	$168.50
7 purchase totals =	$1,122.08		$1,219.9372	$1,219.94	$1,219.90	$1,220.00