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	$100.29	4.798%	$105.1019	$105.10	$105.10	$105.10
Purchase #2	$171.37	8.815%	$186.4763	$186.48	$186.50	$186.50
Purchase #3	$6.49	8.495%	$7.0413	$7.04	$7.05	$7.00
Purchase #4	$23.87	13.365%	$27.0602	$27.06	$27.05	$27.10
Purchase #5	$34.90	4.739%	$36.5539	$36.55	$36.55	$36.60
Purchase #6	$78.45	11.446%	$87.4294	$87.43	$87.45	$87.40
Purchase #7	$125.53	4.865%	$131.637	$131.64	$131.65	$131.60
7 purchase totals =	$540.90		$581.3000	$581.30	$581.35	$581.30