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	$191.72	9.277%	$209.5059	$209.51	$209.50	$209.50
Purchase #2	$63.65	10.472%	$70.3154	$70.32	$70.30	$70.30
Purchase #3	$186.45	5.222%	$196.1864	$196.19	$196.20	$196.20
Purchase #4	$178.31	8.179%	$192.894	$192.89	$192.90	$192.90
Purchase #5	$27.41	11.649%	$30.603	$30.60	$30.60	$30.60
Purchase #6	$31.87	4.544%	$33.3182	$33.32	$33.30	$33.30
Purchase #7	$177.46	5.690%	$187.5575	$187.56	$187.55	$187.60
7 purchase totals =	$856.87		$920.3804	$920.39	$920.35	$920.40