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	$131.44	7.562%	$141.3795	$141.38	$141.40	$141.40
Purchase #2	$153.98	11.624%	$171.8786	$171.88	$171.90	$171.90
Purchase #3	$53.76	10.437%	$59.3709	$59.37	$59.35	$59.40
Purchase #4	$46.63	7.114%	$49.9473	$49.95	$49.95	$49.90
Purchase #5	$91.73	9.572%	$100.5104	$100.51	$100.50	$100.50
Purchase #6	$185.88	13.253%	$210.5147	$210.51	$210.50	$210.50
Purchase #7	$141.50	5.488%	$149.2655	$149.27	$149.25	$149.30
7 purchase totals =	$804.92		$882.8669	$882.87	$882.85	$882.90