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	$82.94	10.838%	$91.929	$91.93	$91.95	$91.90
Purchase #2	$118.67	4.404%	$123.8962	$123.90	$123.90	$123.90
Purchase #3	$33.99	9.599%	$37.2527	$37.25	$37.25	$37.30
Purchase #4	$97.42	10.464%	$107.614	$107.61	$107.60	$107.60
Purchase #5	$84.44	3.626%	$87.5018	$87.50	$87.50	$87.50
Purchase #6	$68.86	9.787%	$75.5993	$75.60	$75.60	$75.60
Purchase #7	$145.28	11.850%	$162.4957	$162.50	$162.50	$162.50
7 purchase totals =	$631.60		$686.2887	$686.29	$686.30	$686.30