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	$88.97	3.674%	$92.2388	$92.24	$92.25	$92.20
Purchase #2	$154.90	10.495%	$171.1568	$171.16	$171.15	$171.20
Purchase #3	$113.45	13.281%	$128.5173	$128.52	$128.50	$128.50
Purchase #4	$70.32	8.442%	$76.2564	$76.26	$76.25	$76.30
Purchase #5	$98.60	11.392%	$109.8325	$109.83	$109.85	$109.80
Purchase #6	$106.55	12.253%	$119.6056	$119.61	$119.60	$119.60
Purchase #7	$108.79	7.155%	$116.5739	$116.57	$116.55	$116.60
7 purchase totals =	$741.58		$814.1813	$814.19	$814.15	$814.20