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	$93.88	4.218%	$97.8399	$97.84	$97.85	$97.80
Purchase #2	$7.42	5.862%	$7.855	$7.86	$7.85	$7.90
Purchase #3	$226.98	7.260%	$243.4587	$243.46	$243.45	$243.50
Purchase #4	$12.46	5.133%	$13.0996	$13.10	$13.10	$13.10
Purchase #5	$228.78	11.693%	$255.5312	$255.53	$255.55	$255.50
Purchase #6	$89.89	12.228%	$100.8817	$100.88	$100.90	$100.90
Purchase #7	$145.37	6.759%	$155.1956	$155.20	$155.20	$155.20
7 purchase totals =	$804.78		$873.8617	$873.87	$873.90	$873.90