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	$210.38	12.721%	$237.1424	$237.14	$237.15	$237.10
Purchase #2	$65.76	3.230%	$67.884	$67.88	$67.90	$67.90
Purchase #3	$175.43	4.562%	$183.4331	$183.43	$183.45	$183.40
Purchase #4	$103.73	7.355%	$111.3593	$111.36	$111.35	$111.40
Purchase #5	$158.96	9.206%	$173.5939	$173.59	$173.60	$173.60
Purchase #6	$96.94	9.115%	$105.7761	$105.78	$105.80	$105.80
Purchase #7	$144.51	13.385%	$163.8527	$163.85	$163.85	$163.90
7 purchase totals =	$955.71		$1,043.0415	$1,043.03	$1,043.10	$1,043.10