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	$118.97	7.574%	$127.9808	$127.98	$128.00	$128.00
Purchase #2	$237.65	7.443%	$255.3383	$255.34	$255.35	$255.30
Purchase #3	$161.76	10.251%	$178.342	$178.34	$178.35	$178.30
Purchase #4	$29.98	5.852%	$31.7344	$31.73	$31.75	$31.70
Purchase #5	$80.25	3.430%	$83.0026	$83.00	$83.00	$83.00
Purchase #6	$171.48	5.313%	$180.5907	$180.59	$180.60	$180.60
Purchase #7	$41.27	3.639%	$42.7718	$42.77	$42.75	$42.80
7 purchase totals =	$841.36		$899.7606	$899.75	$899.80	$899.70