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	$87.88	5.593%	$92.7951	$92.80	$92.80	$92.80
Purchase #2	$194.60	4.580%	$203.5127	$203.51	$203.50	$203.50
Purchase #3	$39.89	11.423%	$44.4466	$44.45	$44.45	$44.40
Purchase #4	$61.38	5.748%	$64.9081	$64.91	$64.90	$64.90
Purchase #5	$12.34	6.210%	$13.1063	$13.11	$13.10	$13.10
Purchase #6	$136.44	5.851%	$144.4231	$144.42	$144.40	$144.40
Purchase #7	$57.98	12.789%	$65.3951	$65.40	$65.40	$65.40
7 purchase totals =	$590.51		$628.5870	$628.60	$628.55	$628.50