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	$147.26	13.475%	$167.1033	$167.10	$167.10	$167.10
Purchase #2	$42.47	10.458%	$46.9115	$46.91	$46.90	$46.90
Purchase #3	$165.53	12.800%	$186.7178	$186.72	$186.70	$186.70
Purchase #4	$86.48	6.323%	$91.9481	$91.95	$91.95	$91.90
Purchase #5	$115.54	7.223%	$123.8855	$123.89	$123.90	$123.90
Purchase #6	$45.35	10.664%	$50.1861	$50.19	$50.20	$50.20
Purchase #7	$139.42	5.666%	$147.3195	$147.32	$147.30	$147.30
7 purchase totals =	$742.05		$814.0718	$814.08	$814.05	$814.00