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	$137.73	13.649%	$156.5288	$156.53	$156.55	$156.50
Purchase #2	$172.71	3.736%	$179.1624	$179.16	$179.15	$179.20
Purchase #3	$136.48	7.281%	$146.4171	$146.42	$146.40	$146.40
Purchase #4	$238.37	6.450%	$253.7449	$253.74	$253.75	$253.70
Purchase #5	$118.92	5.776%	$125.7888	$125.79	$125.80	$125.80
Purchase #6	$76.90	7.442%	$82.6229	$82.62	$82.60	$82.60
Purchase #7	$192.78	8.678%	$209.5094	$209.51	$209.50	$209.50
7 purchase totals =	$1,073.89		$1,153.7743	$1,153.77	$1,153.75	$1,153.70