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	$199.65	8.181%	$215.9834	$215.98	$216.00	$216.00
Purchase #2	$47.54	8.864%	$51.7539	$51.75	$51.75	$51.80
Purchase #3	$101.55	3.760%	$105.3683	$105.37	$105.35	$105.40
Purchase #4	$229.86	11.104%	$255.3837	$255.38	$255.40	$255.40
Purchase #5	$128.84	7.750%	$138.8251	$138.83	$138.85	$138.80
Purchase #6	$168.34	11.155%	$187.1183	$187.12	$187.10	$187.10
Purchase #7	$76.55	5.686%	$80.9026	$80.90	$80.90	$80.90
7 purchase totals =	$952.33		$1,035.3353	$1,035.33	$1,035.35	$1,035.40