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	$93.64	4.748%	$98.086	$98.09	$98.10	$98.10
Purchase #2	$144.37	6.129%	$153.2184	$153.22	$153.20	$153.20
Purchase #3	$67.96	5.859%	$71.9418	$71.94	$71.95	$71.90
Purchase #4	$35.55	13.257%	$40.2629	$40.26	$40.25	$40.30
Purchase #5	$175.50	11.868%	$196.3283	$196.33	$196.35	$196.30
Purchase #6	$13.89	12.855%	$15.6756	$15.68	$15.70	$15.70
Purchase #7	$44.76	9.228%	$48.8905	$48.89	$48.90	$48.90
7 purchase totals =	$575.67		$624.4035	$624.41	$624.45	$624.40