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	$45.84	12.486%	$51.5636	$51.56	$51.55	$51.60
Purchase #2	$148.31	5.704%	$156.7696	$156.77	$156.75	$156.80
Purchase #3	$218.28	11.288%	$242.9194	$242.92	$242.90	$242.90
Purchase #4	$83.59	8.651%	$90.8214	$90.82	$90.80	$90.80
Purchase #5	$135.88	5.288%	$143.0653	$143.07	$143.05	$143.10
Purchase #6	$205.67	13.439%	$233.31	$233.31	$233.30	$233.30
Purchase #7	$107.50	5.814%	$113.7501	$113.75	$113.75	$113.80
7 purchase totals =	$945.07		$1,032.1994	$1,032.20	$1,032.10	$1,032.30