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	$61.83	9.118%	$67.4677	$67.47	$67.45	$67.50
Purchase #2	$5.92	12.184%	$6.6413	$6.64	$6.65	$6.60
Purchase #3	$192.88	10.270%	$212.6888	$212.69	$212.70	$212.70
Purchase #4	$211.63	3.851%	$219.7799	$219.78	$219.80	$219.80
Purchase #5	$126.66	7.731%	$136.4521	$136.45	$136.45	$136.50
Purchase #6	$34.81	8.553%	$37.7873	$37.79	$37.80	$37.80
Purchase #7	$75.55	13.146%	$85.4818	$85.48	$85.50	$85.50
7 purchase totals =	$709.28		$766.2989	$766.30	$766.35	$766.40