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	$147.47	13.559%	$167.4655	$167.47	$167.45	$167.50
Purchase #2	$104.51	3.765%	$108.4448	$108.44	$108.45	$108.40
Purchase #3	$19.33	3.482%	$20.0031	$20.00	$20.00	$20.00
Purchase #4	$30.57	4.247%	$31.8683	$31.87	$31.85	$31.90
Purchase #5	$130.44	8.801%	$141.92	$141.92	$141.90	$141.90
Purchase #6	$200.63	3.115%	$206.8796	$206.88	$206.90	$206.90
Purchase #7	$209.89	4.502%	$219.3392	$219.34	$219.35	$219.30
7 purchase totals =	$842.84		$895.9205	$895.92	$895.90	$895.90