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	$126.98	4.768%	$133.0344	$133.03	$133.05	$133.00
Purchase #2	$139.83	6.164%	$148.4491	$148.45	$148.45	$148.40
Purchase #3	$169.32	11.287%	$188.4311	$188.43	$188.45	$188.40
Purchase #4	$119.56	7.517%	$128.5473	$128.55	$128.55	$128.50
Purchase #5	$36.32	8.647%	$39.4606	$39.46	$39.45	$39.50
Purchase #6	$97.37	7.689%	$104.8568	$104.86	$104.85	$104.90
Purchase #7	$35.95	6.854%	$38.414	$38.41	$38.40	$38.40
7 purchase totals =	$725.33		$781.1933	$781.19	$781.20	$781.10