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	$36.31	3.458%	$37.5656	$37.57	$37.55	$37.60
Purchase #2	$124.37	11.867%	$139.129	$139.13	$139.15	$139.10
Purchase #3	$173.32	7.798%	$186.8355	$186.84	$186.85	$186.80
Purchase #4	$147.28	11.459%	$164.1568	$164.16	$164.15	$164.20
Purchase #5	$7.81	9.636%	$8.5626	$8.56	$8.55	$8.60
Purchase #6	$65.77	7.799%	$70.8994	$70.90	$70.90	$70.90
Purchase #7	$150.94	5.300%	$158.9398	$158.94	$158.95	$158.90
7 purchase totals =	$705.80		$766.0887	$766.10	$766.10	$766.10