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	$165.48	11.851%	$185.091	$185.09	$185.10	$185.10
Purchase #2	$19.81	6.209%	$21.04	$21.04	$21.05	$21.00
Purchase #3	$47.40	9.511%	$51.9082	$51.91	$51.90	$51.90
Purchase #4	$188.95	10.163%	$208.153	$208.15	$208.15	$208.20
Purchase #5	$109.80	12.138%	$123.1275	$123.13	$123.15	$123.10
Purchase #6	$123.98	13.135%	$140.2648	$140.26	$140.25	$140.30
Purchase #7	$152.25	4.735%	$159.459	$159.46	$159.45	$159.50
7 purchase totals =	$807.67		$889.0435	$889.04	$889.05	$889.10