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	$29.41	8.635%	$31.9496	$31.95	$31.95	$31.90
Purchase #2	$46.32	13.190%	$52.4296	$52.43	$52.45	$52.40
Purchase #3	$92.34	3.872%	$95.9154	$95.92	$95.90	$95.90
Purchase #4	$138.90	4.222%	$144.7644	$144.76	$144.75	$144.80
Purchase #5	$205.33	3.468%	$212.4508	$212.45	$212.45	$212.50
Purchase #6	$103.47	4.472%	$108.0972	$108.10	$108.10	$108.10
Purchase #7	$123.56	8.679%	$134.2838	$134.28	$134.30	$134.30
7 purchase totals =	$739.33		$779.8908	$779.89	$779.90	$779.90