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	$129.82	13.739%	$147.656	$147.66	$147.65	$147.70
Purchase #2	$250.90	10.723%	$277.804	$277.80	$277.80	$277.80
Purchase #3	$158.57	11.545%	$176.8769	$176.88	$176.90	$176.90
Purchase #4	$8.56	12.214%	$9.6055	$9.61	$9.60	$9.60
Purchase #5	$73.25	7.342%	$78.628	$78.63	$78.65	$78.60
Purchase #6	$172.60	6.277%	$183.4341	$183.43	$183.45	$183.40
Purchase #7	$124.59	5.555%	$131.511	$131.51	$131.50	$131.50
7 purchase totals =	$918.29		$1,005.5155	$1,005.52	$1,005.55	$1,005.50