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	$224.73	7.452%	$241.4769	$241.48	$241.50	$241.50
Purchase #2	$90.43	6.495%	$96.3034	$96.30	$96.30	$96.30
Purchase #3	$42.62	7.477%	$45.8067	$45.81	$45.80	$45.80
Purchase #4	$159.66	12.304%	$179.3046	$179.30	$179.30	$179.30
Purchase #5	$65.54	11.833%	$73.2953	$73.30	$73.30	$73.30
Purchase #6	$209.89	13.528%	$238.2839	$238.28	$238.30	$238.30
Purchase #7	$225.48	6.759%	$240.7202	$240.72	$240.70	$240.70
7 purchase totals =	$1,018.35		$1,115.1910	$1,115.19	$1,115.20	$1,115.20