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	$132.37	10.256%	$145.9459	$145.95	$145.95	$145.90
Purchase #2	$101.50	5.354%	$106.9343	$106.93	$106.95	$106.90
Purchase #3	$118.57	6.159%	$125.8727	$125.87	$125.85	$125.90
Purchase #4	$229.89	13.274%	$260.4056	$260.41	$260.40	$260.40
Purchase #5	$84.39	7.325%	$90.5716	$90.57	$90.55	$90.60
Purchase #6	$250.77	5.385%	$264.274	$264.27	$264.25	$264.30
Purchase #7	$245.33	6.637%	$261.6126	$261.61	$261.60	$261.60
7 purchase totals =	$1,162.82		$1,255.6167	$1,255.61	$1,255.55	$1,255.60