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	$91.25	13.144%	$103.2439	$103.24	$103.25	$103.20
Purchase #2	$121.25	8.197%	$131.1889	$131.19	$131.20	$131.20
Purchase #3	$94.72	5.629%	$100.0518	$100.05	$100.05	$100.10
Purchase #4	$154.80	7.573%	$166.523	$166.52	$166.50	$166.50
Purchase #5	$37.99	9.659%	$41.6595	$41.66	$41.65	$41.70
Purchase #6	$133.77	12.680%	$150.732	$150.73	$150.75	$150.70
Purchase #7	$36.32	11.586%	$40.528	$40.53	$40.55	$40.50
7 purchase totals =	$670.10		$733.9271	$733.92	$733.95	$733.90