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	$116.94	5.488%	$123.3577	$123.36	$123.35	$123.40
Purchase #2	$93.78	5.675%	$99.102	$99.10	$99.10	$99.10
Purchase #3	$169.73	12.825%	$191.4979	$191.50	$191.50	$191.50
Purchase #4	$162.62	8.783%	$176.9029	$176.90	$176.90	$176.90
Purchase #5	$243.80	9.143%	$266.0906	$266.09	$266.10	$266.10
Purchase #6	$155.49	3.710%	$161.2587	$161.26	$161.25	$161.30
Purchase #7	$40.59	3.533%	$42.024	$42.02	$42.00	$42.00
7 purchase totals =	$982.95		$1,060.2338	$1,060.23	$1,060.20	$1,060.30