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	$42.68	8.507%	$46.3108	$46.31	$46.30	$46.30
Purchase #2	$244.98	4.475%	$255.9429	$255.94	$255.95	$255.90
Purchase #3	$87.51	13.709%	$99.5067	$99.51	$99.50	$99.50
Purchase #4	$177.86	6.423%	$189.2839	$189.28	$189.30	$189.30
Purchase #5	$135.83	7.260%	$145.6913	$145.69	$145.70	$145.70
Purchase #6	$217.66	10.759%	$241.078	$241.08	$241.10	$241.10
Purchase #7	$136.65	4.486%	$142.7801	$142.78	$142.80	$142.80
7 purchase totals =	$1,043.17		$1,120.5937	$1,120.59	$1,120.65	$1,120.60