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	$224.51	8.376%	$243.315	$243.32	$243.30	$243.30
Purchase #2	$79.37	5.602%	$83.8163	$83.82	$83.80	$83.80
Purchase #3	$234.50	12.813%	$264.5465	$264.55	$264.55	$264.50
Purchase #4	$147.44	3.245%	$152.2244	$152.22	$152.20	$152.20
Purchase #5	$239.93	4.554%	$250.8564	$250.86	$250.85	$250.90
Purchase #6	$92.79	12.635%	$104.514	$104.51	$104.50	$104.50
Purchase #7	$18.81	8.516%	$20.4119	$20.41	$20.40	$20.40
7 purchase totals =	$1,037.35		$1,119.6845	$1,119.69	$1,119.60	$1,119.60