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	$133.38	8.825%	$145.1508	$145.15	$145.15	$145.20
Purchase #2	$180.83	8.672%	$196.5116	$196.51	$196.50	$196.50
Purchase #3	$219.28	11.873%	$245.3151	$245.32	$245.30	$245.30
Purchase #4	$52.51	7.175%	$56.2776	$56.28	$56.30	$56.30
Purchase #5	$45.89	8.261%	$49.681	$49.68	$49.70	$49.70
Purchase #6	$150.42	9.228%	$164.3008	$164.30	$164.30	$164.30
Purchase #7	$70.61	6.715%	$75.3515	$75.35	$75.35	$75.40
7 purchase totals =	$852.92		$932.5884	$932.59	$932.60	$932.70