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	$182.55	12.517%	$205.3998	$205.40	$205.40	$205.40
Purchase #2	$43.51	6.240%	$46.225	$46.23	$46.25	$46.20
Purchase #3	$24.59	7.783%	$26.5038	$26.50	$26.50	$26.50
Purchase #4	$141.86	8.272%	$153.5947	$153.59	$153.60	$153.60
Purchase #5	$160.55	13.463%	$182.1648	$182.16	$182.15	$182.20
Purchase #6	$94.75	11.440%	$105.5894	$105.59	$105.60	$105.60
Purchase #7	$65.88	10.643%	$72.8916	$72.89	$72.90	$72.90
7 purchase totals =	$713.69		$792.3691	$792.36	$792.40	$792.40