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	$239.48	12.494%	$269.4006	$269.40	$269.40	$269.40
Purchase #2	$90.35	5.488%	$95.3084	$95.31	$95.30	$95.30
Purchase #3	$190.50	4.382%	$198.8477	$198.85	$198.85	$198.80
Purchase #4	$35.46	6.789%	$37.8674	$37.87	$37.85	$37.90
Purchase #5	$168.48	9.740%	$184.89	$184.89	$184.90	$184.90
Purchase #6	$222.25	9.794%	$244.0172	$244.02	$244.00	$244.00
Purchase #7	$153.58	5.610%	$162.1958	$162.20	$162.20	$162.20
7 purchase totals =	$1,100.10		$1,192.5271	$1,192.54	$1,192.50	$1,192.50