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	$117.38	12.360%	$131.8882	$131.89	$131.90	$131.90
Purchase #2	$147.55	13.796%	$167.906	$167.91	$167.90	$167.90
Purchase #3	$144.47	8.305%	$156.4682	$156.47	$156.45	$156.50
Purchase #4	$171.42	6.160%	$181.9795	$181.98	$182.00	$182.00
Purchase #5	$188.36	13.340%	$213.4872	$213.49	$213.50	$213.50
Purchase #6	$48.83	11.472%	$54.4318	$54.43	$54.45	$54.40
Purchase #7	$148.72	3.463%	$153.8702	$153.87	$153.85	$153.90
7 purchase totals =	$966.73		$1,060.0311	$1,060.04	$1,060.05	$1,060.10