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	$175.48	9.106%	$191.4592	$191.46	$191.45	$191.50
Purchase #2	$18.71	9.768%	$20.5376	$20.54	$20.55	$20.50
Purchase #3	$57.50	8.139%	$62.1799	$62.18	$62.20	$62.20
Purchase #4	$92.77	11.590%	$103.522	$103.52	$103.50	$103.50
Purchase #5	$45.31	4.840%	$47.503	$47.50	$47.50	$47.50
Purchase #6	$98.71	6.862%	$105.4835	$105.48	$105.50	$105.50
Purchase #7	$171.84	10.255%	$189.4622	$189.46	$189.45	$189.50
7 purchase totals =	$660.32		$720.1474	$720.14	$720.15	$720.20