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	$30.26	10.581%	$33.4618	$33.46	$33.45	$33.50
Purchase #2	$6.84	3.716%	$7.0942	$7.09	$7.10	$7.10
Purchase #3	$151.78	4.529%	$158.6541	$158.65	$158.65	$158.70
Purchase #4	$198.84	3.866%	$206.5272	$206.53	$206.55	$206.50
Purchase #5	$89.82	11.730%	$100.3559	$100.36	$100.35	$100.40
Purchase #6	$47.87	13.334%	$54.253	$54.25	$54.25	$54.30
Purchase #7	$26.27	9.466%	$28.7567	$28.76	$28.75	$28.80
7 purchase totals =	$551.68		$589.1029	$589.10	$589.10	$589.30