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	$49.52	4.805%	$51.8994	$51.90	$51.90	$51.90
Purchase #2	$250.82	11.823%	$280.4744	$280.47	$280.45	$280.50
Purchase #3	$82.88	12.160%	$92.9582	$92.96	$92.95	$93.00
Purchase #4	$63.76	3.651%	$66.0879	$66.09	$66.10	$66.10
Purchase #5	$189.95	3.431%	$196.4672	$196.47	$196.45	$196.50
Purchase #6	$247.54	6.650%	$264.0014	$264.00	$264.00	$264.00
Purchase #7	$239.72	3.735%	$248.6735	$248.67	$248.65	$248.70
7 purchase totals =	$1,124.19		$1,200.5620	$1,200.56	$1,200.50	$1,200.70