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	$33.48	12.346%	$37.6134	$37.61	$37.60	$37.60
Purchase #2	$182.80	7.427%	$196.3766	$196.38	$196.40	$196.40
Purchase #3	$52.80	4.302%	$55.0715	$55.07	$55.05	$55.10
Purchase #4	$91.76	5.682%	$96.9738	$96.97	$96.95	$97.00
Purchase #5	$119.87	6.478%	$127.6352	$127.64	$127.65	$127.60
Purchase #6	$156.49	7.684%	$168.5147	$168.51	$168.50	$168.50
Purchase #7	$199.97	8.460%	$216.8875	$216.89	$216.90	$216.90
7 purchase totals =	$837.17		$899.0727	$899.07	$899.05	$899.10