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	$129.76	11.640%	$144.8641	$144.86	$144.85	$144.90
Purchase #2	$35.48	3.318%	$36.6572	$36.66	$36.65	$36.70
Purchase #3	$184.26	3.506%	$190.7202	$190.72	$190.70	$190.70
Purchase #4	$91.42	10.845%	$101.3345	$101.33	$101.35	$101.30
Purchase #5	$6.59	12.737%	$7.4294	$7.43	$7.45	$7.40
Purchase #6	$83.84	6.792%	$89.5344	$89.53	$89.55	$89.50
Purchase #7	$54.50	3.738%	$56.5372	$56.54	$56.55	$56.50
7 purchase totals =	$585.85		$627.0770	$627.07	$627.10	$627.00