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	$194.44	12.339%	$218.432	$218.43	$218.45	$218.40
Purchase #2	$238.30	8.730%	$259.1036	$259.10	$259.10	$259.10
Purchase #3	$31.48	4.222%	$32.8091	$32.81	$32.80	$32.80
Purchase #4	$13.76	5.493%	$14.5158	$14.52	$14.50	$14.50
Purchase #5	$205.59	8.371%	$222.7999	$222.80	$222.80	$222.80
Purchase #6	$195.66	6.483%	$208.3446	$208.34	$208.35	$208.30
Purchase #7	$55.65	11.187%	$61.8756	$61.88	$61.90	$61.90
7 purchase totals =	$934.88		$1,017.8806	$1,017.88	$1,017.90	$1,017.80