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	$23.59	5.352%	$24.8525	$24.85	$24.85	$24.90
Purchase #2	$105.73	4.242%	$110.2151	$110.22	$110.20	$110.20
Purchase #3	$172.77	13.777%	$196.5725	$196.57	$196.55	$196.60
Purchase #4	$234.87	13.512%	$266.6056	$266.61	$266.60	$266.60
Purchase #5	$169.58	12.388%	$190.5876	$190.59	$190.60	$190.60
Purchase #6	$53.73	12.120%	$60.2421	$60.24	$60.25	$60.20
Purchase #7	$80.50	6.765%	$85.9458	$85.95	$85.95	$85.90
7 purchase totals =	$840.77		$935.0212	$935.03	$935.00	$935.00