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	$218.66	11.532%	$243.8759	$243.88	$243.90	$243.90
Purchase #2	$156.84	12.127%	$175.86	$175.86	$175.85	$175.90
Purchase #3	$30.33	7.544%	$32.6181	$32.62	$32.60	$32.60
Purchase #4	$143.56	5.103%	$150.8859	$150.89	$150.90	$150.90
Purchase #5	$139.98	10.604%	$154.8235	$154.82	$154.80	$154.80
Purchase #6	$150.79	11.274%	$167.7901	$167.79	$167.80	$167.80
Purchase #7	$34.54	6.116%	$36.6525	$36.65	$36.65	$36.70
7 purchase totals =	$874.70		$962.5060	$962.51	$962.50	$962.60