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	$53.59	4.574%	$56.0412	$56.04	$56.05	$56.00
Purchase #2	$188.96	13.491%	$214.4526	$214.45	$214.45	$214.50
Purchase #3	$203.70	5.356%	$214.6102	$214.61	$214.60	$214.60
Purchase #4	$42.91	3.158%	$44.2651	$44.27	$44.25	$44.30
Purchase #5	$136.30	3.275%	$140.7638	$140.76	$140.75	$140.80
Purchase #6	$160.29	6.840%	$171.2538	$171.25	$171.25	$171.30
Purchase #7	$226.25	9.565%	$247.8908	$247.89	$247.90	$247.90
7 purchase totals =	$1,012.00		$1,089.2775	$1,089.27	$1,089.25	$1,089.40