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	$167.96	11.235%	$186.8303	$186.83	$186.85	$186.80
Purchase #2	$19.66	3.683%	$20.3841	$20.38	$20.40	$20.40
Purchase #3	$125.97	4.722%	$131.9183	$131.92	$131.90	$131.90
Purchase #4	$26.39	3.441%	$27.2981	$27.30	$27.30	$27.30
Purchase #5	$198.61	9.162%	$216.8066	$216.81	$216.80	$216.80
Purchase #6	$99.76	11.284%	$111.0169	$111.02	$111.00	$111.00
Purchase #7	$187.25	4.692%	$196.0358	$196.04	$196.05	$196.00
7 purchase totals =	$825.60		$890.2901	$890.30	$890.30	$890.20