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	$94.84	7.190%	$101.659	$101.66	$101.65	$101.70
Purchase #2	$184.90	10.776%	$204.8248	$204.82	$204.80	$204.80
Purchase #3	$100.27	9.117%	$109.4116	$109.41	$109.40	$109.40
Purchase #4	$37.75	7.510%	$40.585	$40.59	$40.60	$40.60
Purchase #5	$161.91	4.265%	$168.8155	$168.82	$168.80	$168.80
Purchase #6	$243.98	4.436%	$254.803	$254.80	$254.80	$254.80
Purchase #7	$25.55	5.140%	$26.8633	$26.86	$26.85	$26.90
7 purchase totals =	$849.20		$906.9622	$906.96	$906.90	$907.00