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	$32.72	4.752%	$34.2749	$34.27	$34.25	$34.30
Purchase #2	$70.29	3.728%	$72.9104	$72.91	$72.90	$72.90
Purchase #3	$179.76	5.825%	$190.231	$190.23	$190.25	$190.20
Purchase #4	$160.54	4.759%	$168.1801	$168.18	$168.20	$168.20
Purchase #5	$245.78	5.599%	$259.5412	$259.54	$259.55	$259.50
Purchase #6	$159.29	3.570%	$164.9767	$164.98	$165.00	$165.00
Purchase #7	$34.89	3.484%	$36.1056	$36.11	$36.10	$36.10
7 purchase totals =	$883.27		$926.2199	$926.22	$926.25	$926.20