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	$57.53	5.235%	$60.5417	$60.54	$60.55	$60.50
Purchase #2	$198.59	6.691%	$211.8777	$211.88	$211.90	$211.90
Purchase #3	$136.69	4.863%	$143.3372	$143.34	$143.35	$143.30
Purchase #4	$185.56	13.807%	$211.1803	$211.18	$211.20	$211.20
Purchase #5	$246.83	7.248%	$264.7202	$264.72	$264.70	$264.70
Purchase #6	$84.86	6.850%	$90.6729	$90.67	$90.65	$90.70
Purchase #7	$63.83	9.711%	$70.0285	$70.03	$70.05	$70.00
7 purchase totals =	$973.89		$1,052.3585	$1,052.36	$1,052.40	$1,052.30