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	$240.70	11.176%	$267.6006	$267.60	$267.60	$267.60
Purchase #2	$58.36	5.553%	$61.6007	$61.60	$61.60	$61.60
Purchase #3	$87.82	11.137%	$97.6005	$97.60	$97.60	$97.60
Purchase #4	$55.88	3.695%	$57.9448	$57.94	$57.95	$57.90
Purchase #5	$23.51	3.651%	$24.3684	$24.37	$24.35	$24.40
Purchase #6	$72.48	7.629%	$78.0095	$78.01	$78.00	$78.00
Purchase #7	$79.69	7.834%	$85.9329	$85.93	$85.95	$85.90
7 purchase totals =	$618.44		$673.0574	$673.05	$673.05	$673.00