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	$91.86	10.807%	$101.7873	$101.79	$101.80	$101.80
Purchase #2	$100.75	9.688%	$110.5107	$110.51	$110.50	$110.50
Purchase #3	$58.42	5.210%	$61.4637	$61.46	$61.45	$61.50
Purchase #4	$244.41	8.195%	$264.4394	$264.44	$264.45	$264.40
Purchase #5	$172.82	13.277%	$195.7653	$195.77	$195.75	$195.80
Purchase #6	$28.81	12.725%	$32.4761	$32.48	$32.50	$32.50
Purchase #7	$35.92	5.463%	$37.8823	$37.88	$37.90	$37.90
7 purchase totals =	$732.99		$804.3248	$804.33	$804.35	$804.40