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	$175.86	5.137%	$184.8939	$184.89	$184.90	$184.90
Purchase #2	$105.56	13.288%	$119.5868	$119.59	$119.60	$119.60
Purchase #3	$241.34	9.774%	$264.9286	$264.93	$264.95	$264.90
Purchase #4	$99.54	13.356%	$112.8346	$112.83	$112.85	$112.80
Purchase #5	$157.82	9.776%	$173.2485	$173.25	$173.25	$173.20
Purchase #6	$95.94	4.142%	$99.9138	$99.91	$99.90	$99.90
Purchase #7	$187.38	5.870%	$198.3792	$198.38	$198.40	$198.40
7 purchase totals =	$1,063.44		$1,153.7854	$1,153.78	$1,153.85	$1,153.70