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	$111.97	3.135%	$115.4803	$115.48	$115.50	$115.50
Purchase #2	$29.79	9.307%	$32.5626	$32.56	$32.55	$32.60
Purchase #3	$196.30	7.472%	$210.9675	$210.97	$210.95	$211.00
Purchase #4	$54.37	9.405%	$59.4835	$59.48	$59.50	$59.50
Purchase #5	$40.73	6.750%	$43.4793	$43.48	$43.50	$43.50
Purchase #6	$248.75	5.234%	$261.7696	$261.77	$261.75	$261.80
Purchase #7	$171.86	5.492%	$181.2986	$181.30	$181.30	$181.30
7 purchase totals =	$853.77		$905.0414	$905.04	$905.05	$905.20