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	$180.59	5.793%	$191.0516	$191.05	$191.05	$191.10
Purchase #2	$40.40	12.383%	$45.4027	$45.40	$45.40	$45.40
Purchase #3	$167.48	3.252%	$172.9264	$172.93	$172.95	$172.90
Purchase #4	$123.49	12.677%	$139.1448	$139.14	$139.15	$139.10
Purchase #5	$53.57	4.203%	$55.8215	$55.82	$55.80	$55.80
Purchase #6	$74.61	9.306%	$81.5532	$81.55	$81.55	$81.60
Purchase #7	$113.37	11.739%	$126.6785	$126.68	$126.70	$126.70
7 purchase totals =	$753.51		$812.5787	$812.57	$812.60	$812.60