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	$236.93	5.711%	$250.4611	$250.46	$250.45	$250.50
Purchase #2	$43.47	4.278%	$45.3296	$45.33	$45.35	$45.30
Purchase #3	$13.28	5.295%	$13.9832	$13.98	$14.00	$14.00
Purchase #4	$118.43	6.554%	$126.1919	$126.19	$126.20	$126.20
Purchase #5	$141.36	3.816%	$146.7543	$146.75	$146.75	$146.80
Purchase #6	$66.51	9.586%	$72.8856	$72.89	$72.90	$72.90
Purchase #7	$144.72	12.609%	$162.9677	$162.97	$162.95	$163.00
7 purchase totals =	$764.70		$818.5734	$818.57	$818.60	$818.70