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	$209.25	6.470%	$222.7885	$222.79	$222.80	$222.80
Purchase #2	$205.28	5.869%	$217.3279	$217.33	$217.35	$217.30
Purchase #3	$116.47	5.784%	$123.2066	$123.21	$123.20	$123.20
Purchase #4	$55.59	3.698%	$57.6457	$57.65	$57.65	$57.60
Purchase #5	$37.73	13.201%	$42.7107	$42.71	$42.70	$42.70
Purchase #6	$95.41	8.302%	$103.3309	$103.33	$103.35	$103.30
Purchase #7	$225.71	10.401%	$249.1861	$249.19	$249.20	$249.20
7 purchase totals =	$945.44		$1,016.1964	$1,016.21	$1,016.25	$1,016.10