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	$167.42	10.806%	$185.5114	$185.51	$185.50	$185.50
Purchase #2	$86.96	10.550%	$96.1343	$96.13	$96.15	$96.10
Purchase #3	$163.83	5.587%	$172.9832	$172.98	$173.00	$173.00
Purchase #4	$56.78	11.503%	$63.3114	$63.31	$63.30	$63.30
Purchase #5	$206.32	7.504%	$221.8023	$221.80	$221.80	$221.80
Purchase #6	$122.47	7.561%	$131.73	$131.73	$131.75	$131.70
Purchase #7	$203.25	3.290%	$209.9369	$209.94	$209.95	$209.90
7 purchase totals =	$1,007.03		$1,081.4095	$1,081.40	$1,081.45	$1,081.30