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	$196.75	9.554%	$215.5475	$215.55	$215.55	$215.50
Purchase #2	$99.55	12.142%	$111.6374	$111.64	$111.65	$111.60
Purchase #3	$191.46	8.185%	$207.131	$207.13	$207.15	$207.10
Purchase #4	$77.36	13.217%	$87.5847	$87.58	$87.60	$87.60
Purchase #5	$7.57	7.394%	$8.1297	$8.13	$8.15	$8.10
Purchase #6	$129.54	11.498%	$144.4345	$144.43	$144.45	$144.40
Purchase #7	$74.56	5.191%	$78.4304	$78.43	$78.45	$78.40
7 purchase totals =	$776.79		$852.8952	$852.89	$853.00	$852.70