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	$162.88	9.175%	$177.8242	$177.82	$177.80	$177.80
Purchase #2	$84.27	3.145%	$86.9203	$86.92	$86.90	$86.90
Purchase #3	$165.83	3.275%	$171.2609	$171.26	$171.25	$171.30
Purchase #4	$43.67	8.729%	$47.482	$47.48	$47.50	$47.50
Purchase #5	$164.63	8.802%	$179.1207	$179.12	$179.10	$179.10
Purchase #6	$169.35	12.462%	$190.4544	$190.45	$190.45	$190.50
Purchase #7	$52.35	13.718%	$59.5314	$59.53	$59.55	$59.50
7 purchase totals =	$842.98		$912.5939	$912.58	$912.55	$912.60