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	$162.89	12.722%	$183.6129	$183.61	$183.60	$183.60
Purchase #2	$123.47	6.390%	$131.3597	$131.36	$131.35	$131.40
Purchase #3	$94.49	3.347%	$97.6526	$97.65	$97.65	$97.70
Purchase #4	$47.49	10.661%	$52.5529	$52.55	$52.55	$52.60
Purchase #5	$153.57	7.792%	$165.5362	$165.54	$165.55	$165.50
Purchase #6	$52.27	7.492%	$56.1861	$56.19	$56.20	$56.20
Purchase #7	$69.61	12.680%	$78.4365	$78.44	$78.45	$78.40
7 purchase totals =	$703.79		$765.3369	$765.34	$765.35	$765.40