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	$223.65	5.329%	$235.5683	$235.57	$235.55	$235.60
Purchase #2	$90.30	11.776%	$100.9337	$100.93	$100.95	$100.90
Purchase #3	$74.93	10.437%	$82.7504	$82.75	$82.75	$82.80
Purchase #4	$168.42	9.630%	$184.6388	$184.64	$184.65	$184.60
Purchase #5	$134.96	4.657%	$141.2451	$141.25	$141.25	$141.20
Purchase #6	$38.76	13.327%	$43.9255	$43.93	$43.95	$43.90
Purchase #7	$149.85	12.217%	$168.1572	$168.16	$168.15	$168.20
7 purchase totals =	$880.87		$957.2190	$957.23	$957.25	$957.20