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	$136.40	11.713%	$152.3765	$152.38	$152.40	$152.40
Purchase #2	$91.48	3.860%	$95.0111	$95.01	$95.00	$95.00
Purchase #3	$52.66	5.585%	$55.6011	$55.60	$55.60	$55.60
Purchase #4	$59.78	13.230%	$67.6889	$67.69	$67.70	$67.70
Purchase #5	$170.83	4.774%	$178.9854	$178.99	$179.00	$179.00
Purchase #6	$99.76	5.265%	$105.0124	$105.01	$105.00	$105.00
Purchase #7	$226.65	3.126%	$233.7351	$233.74	$233.75	$233.70
7 purchase totals =	$837.56		$888.4105	$888.42	$888.45	$888.40