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	$46.81	9.479%	$51.2471	$51.25	$51.25	$51.20
Purchase #2	$87.42	13.510%	$99.2304	$99.23	$99.25	$99.20
Purchase #3	$139.29	10.400%	$153.7762	$153.78	$153.80	$153.80
Purchase #4	$183.50	7.196%	$196.7047	$196.70	$196.70	$196.70
Purchase #5	$5.49	6.649%	$5.855	$5.86	$5.85	$5.90
Purchase #6	$69.29	3.390%	$71.6389	$71.64	$71.65	$71.60
Purchase #7	$98.37	6.831%	$105.0897	$105.09	$105.10	$105.10
7 purchase totals =	$630.17		$683.5420	$683.55	$683.60	$683.50