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	$88.57	11.270%	$98.5518	$98.55	$98.55	$98.60
Purchase #2	$30.27	10.208%	$33.36	$33.36	$33.35	$33.40
Purchase #3	$116.57	12.828%	$131.5236	$131.52	$131.50	$131.50
Purchase #4	$185.48	7.547%	$199.4782	$199.48	$199.50	$199.50
Purchase #5	$207.28	12.567%	$233.3289	$233.33	$233.35	$233.30
Purchase #6	$30.57	10.422%	$33.756	$33.76	$33.75	$33.80
Purchase #7	$119.50	9.168%	$130.4558	$130.46	$130.45	$130.50
7 purchase totals =	$778.24		$860.4543	$860.46	$860.45	$860.60