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	$57.27	3.424%	$59.2309	$59.23	$59.25	$59.20
Purchase #2	$84.67	7.371%	$90.911	$90.91	$90.90	$90.90
Purchase #3	$102.34	9.499%	$112.0613	$112.06	$112.05	$112.10
Purchase #4	$133.58	11.433%	$148.8522	$148.85	$148.85	$148.90
Purchase #5	$138.35	6.266%	$147.019	$147.02	$147.00	$147.00
Purchase #6	$13.50	7.591%	$14.5248	$14.52	$14.50	$14.50
Purchase #7	$56.45	7.462%	$60.6623	$60.66	$60.65	$60.70
7 purchase totals =	$586.16		$633.2615	$633.25	$633.20	$633.30