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	$152.26	8.556%	$165.2874	$165.29	$165.30	$165.30
Purchase #2	$250.54	13.790%	$285.0895	$285.09	$285.10	$285.10
Purchase #3	$225.87	4.365%	$235.7292	$235.73	$235.75	$235.70
Purchase #4	$92.43	3.737%	$95.8841	$95.88	$95.90	$95.90
Purchase #5	$108.84	13.131%	$123.1318	$123.13	$123.15	$123.10
Purchase #6	$31.87	4.860%	$33.4189	$33.42	$33.40	$33.40
Purchase #7	$168.43	5.690%	$178.0137	$178.01	$178.00	$178.00
7 purchase totals =	$1,030.24		$1,116.5546	$1,116.55	$1,116.60	$1,116.50