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	$221.93	8.558%	$240.9228	$240.92	$240.90	$240.90
Purchase #2	$164.48	4.751%	$172.2944	$172.29	$172.30	$172.30
Purchase #3	$121.66	8.430%	$131.9159	$131.92	$131.90	$131.90
Purchase #4	$146.30	8.449%	$158.6609	$158.66	$158.65	$158.70
Purchase #5	$95.84	4.240%	$99.9036	$99.90	$99.90	$99.90
Purchase #6	$199.86	4.826%	$209.5052	$209.51	$209.50	$209.50
Purchase #7	$23.44	4.772%	$24.5586	$24.56	$24.55	$24.60
7 purchase totals =	$973.51		$1,037.7614	$1,037.76	$1,037.70	$1,037.80