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	$207.69	3.493%	$214.9446	$214.94	$214.95	$214.90
Purchase #2	$141.72	3.828%	$147.145	$147.15	$147.15	$147.10
Purchase #3	$29.59	11.808%	$33.084	$33.08	$33.10	$33.10
Purchase #4	$115.56	13.378%	$131.0196	$131.02	$131.00	$131.00
Purchase #5	$226.42	12.541%	$254.8153	$254.82	$254.80	$254.80
Purchase #6	$10.96	8.633%	$11.9062	$11.91	$11.90	$11.90
Purchase #7	$72.85	13.108%	$82.3992	$82.40	$82.40	$82.40
7 purchase totals =	$804.79		$875.3139	$875.32	$875.30	$875.20