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	$244.90	6.714%	$261.3426	$261.34	$261.35	$261.30
Purchase #2	$54.48	4.591%	$56.9812	$56.98	$57.00	$57.00
Purchase #3	$144.50	5.447%	$152.3709	$152.37	$152.35	$152.40
Purchase #4	$209.81	10.848%	$232.5702	$232.57	$232.55	$232.60
Purchase #5	$90.28	4.240%	$94.1079	$94.11	$94.10	$94.10
Purchase #6	$141.90	6.531%	$151.1675	$151.17	$151.15	$151.20
Purchase #7	$77.97	6.864%	$83.3219	$83.32	$83.30	$83.30
7 purchase totals =	$963.84		$1,031.8622	$1,031.86	$1,031.80	$1,031.90