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	$90.48	8.388%	$98.0695	$98.07	$98.05	$98.10
Purchase #2	$190.59	7.359%	$204.6155	$204.62	$204.60	$204.60
Purchase #3	$82.39	13.630%	$93.6198	$93.62	$93.60	$93.60
Purchase #4	$218.78	8.297%	$236.9322	$236.93	$236.95	$236.90
Purchase #5	$28.43	11.224%	$31.621	$31.62	$31.60	$31.60
Purchase #6	$170.41	5.828%	$180.3415	$180.34	$180.35	$180.30
Purchase #7	$242.27	5.374%	$255.2896	$255.29	$255.30	$255.30
7 purchase totals =	$1,023.35		$1,100.4891	$1,100.49	$1,100.45	$1,100.40