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	$42.85	5.618%	$45.2573	$45.26	$45.25	$45.30
Purchase #2	$68.34	6.137%	$72.534	$72.53	$72.55	$72.50
Purchase #3	$158.30	3.166%	$163.3118	$163.31	$163.30	$163.30
Purchase #4	$199.61	11.445%	$222.4554	$222.46	$222.45	$222.50
Purchase #5	$34.49	13.511%	$39.1499	$39.15	$39.15	$39.10
Purchase #6	$125.95	6.657%	$134.3345	$134.33	$134.35	$134.30
Purchase #7	$88.29	12.741%	$99.539	$99.54	$99.55	$99.50
7 purchase totals =	$717.83		$776.5819	$776.58	$776.60	$776.50