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	$17.29	11.503%	$19.2789	$19.28	$19.30	$19.30
Purchase #2	$196.83	4.549%	$205.7838	$205.78	$205.80	$205.80
Purchase #3	$89.83	11.591%	$100.2422	$100.24	$100.25	$100.20
Purchase #4	$196.56	4.339%	$205.0887	$205.09	$205.10	$205.10
Purchase #5	$240.78	13.745%	$273.8752	$273.88	$273.90	$273.90
Purchase #6	$242.35	8.774%	$263.6138	$263.61	$263.60	$263.60
Purchase #7	$149.67	12.659%	$168.6167	$168.62	$168.60	$168.60
7 purchase totals =	$1,133.31		$1,236.4993	$1,236.50	$1,236.55	$1,236.50