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	$60.44	11.603%	$67.4529	$67.45	$67.45	$67.50
Purchase #2	$37.89	10.419%	$41.8378	$41.84	$41.85	$41.80
Purchase #3	$118.55	4.316%	$123.6666	$123.67	$123.65	$123.70
Purchase #4	$57.55	13.760%	$65.4689	$65.47	$65.45	$65.50
Purchase #5	$157.46	10.556%	$174.0815	$174.08	$174.10	$174.10
Purchase #6	$247.96	13.316%	$280.9784	$280.98	$281.00	$281.00
Purchase #7	$131.26	6.567%	$139.8798	$139.88	$139.90	$139.90
7 purchase totals =	$811.11		$893.3659	$893.37	$893.40	$893.50