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	$133.29	11.426%	$148.5197	$148.52	$148.50	$148.50
Purchase #2	$14.56	9.559%	$15.9518	$15.95	$15.95	$16.00
Purchase #3	$84.72	12.528%	$95.3337	$95.33	$95.35	$95.30
Purchase #4	$178.71	3.614%	$185.1686	$185.17	$185.15	$185.20
Purchase #5	$122.42	7.382%	$131.457	$131.46	$131.45	$131.50
Purchase #6	$46.54	10.540%	$51.4453	$51.45	$51.45	$51.40
Purchase #7	$147.79	6.519%	$157.4244	$157.42	$157.40	$157.40
7 purchase totals =	$728.03		$785.3005	$785.30	$785.25	$785.30