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	$13.27	11.112%	$14.7446	$14.74	$14.75	$14.70
Purchase #2	$115.90	13.786%	$131.878	$131.88	$131.90	$131.90
Purchase #3	$211.67	13.473%	$240.1883	$240.19	$240.20	$240.20
Purchase #4	$187.63	11.263%	$208.7628	$208.76	$208.75	$208.80
Purchase #5	$208.76	9.160%	$227.8824	$227.88	$227.90	$227.90
Purchase #6	$154.94	11.174%	$172.253	$172.25	$172.25	$172.30
Purchase #7	$14.52	13.849%	$16.5309	$16.53	$16.55	$16.50
7 purchase totals =	$906.69		$1,012.2400	$1,012.23	$1,012.30	$1,012.30