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	$190.60	9.519%	$208.7432	$208.74	$208.75	$208.70
Purchase #2	$157.39	4.145%	$163.9138	$163.91	$163.90	$163.90
Purchase #3	$118.76	4.215%	$123.7657	$123.77	$123.75	$123.80
Purchase #4	$64.90	12.776%	$73.1916	$73.19	$73.20	$73.20
Purchase #5	$203.46	9.348%	$222.4794	$222.48	$222.50	$222.50
Purchase #6	$42.44	7.596%	$45.6637	$45.66	$45.65	$45.70
Purchase #7	$78.54	13.372%	$89.0424	$89.04	$89.05	$89.00
7 purchase totals =	$856.09		$926.7998	$926.79	$926.80	$926.80