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	$84.25	13.217%	$95.3853	$95.39	$95.40	$95.40
Purchase #2	$146.40	11.221%	$162.8275	$162.83	$162.85	$162.80
Purchase #3	$29.50	7.748%	$31.7857	$31.79	$31.80	$31.80
Purchase #4	$52.64	10.839%	$58.3456	$58.35	$58.35	$58.30
Purchase #5	$142.38	6.598%	$151.7742	$151.77	$151.75	$151.80
Purchase #6	$157.44	4.795%	$164.9892	$164.99	$165.00	$165.00
Purchase #7	$149.27	12.648%	$168.1497	$168.15	$168.15	$168.10
7 purchase totals =	$761.88		$833.2572	$833.27	$833.30	$833.20