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	$238.38	6.766%	$254.5088	$254.51	$254.50	$254.50
Purchase #2	$21.87	13.730%	$24.8728	$24.87	$24.85	$24.90
Purchase #3	$90.79	5.519%	$95.8007	$95.80	$95.80	$95.80
Purchase #4	$165.78	12.582%	$186.6384	$186.64	$186.65	$186.60
Purchase #5	$187.77	4.672%	$196.5426	$196.54	$196.55	$196.50
Purchase #6	$175.98	8.471%	$190.8873	$190.89	$190.90	$190.90
Purchase #7	$238.72	9.632%	$261.7135	$261.71	$261.70	$261.70
7 purchase totals =	$1,119.29		$1,210.9641	$1,210.96	$1,210.95	$1,210.90