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	$105.38	7.152%	$112.9168	$112.92	$112.90	$112.90
Purchase #2	$219.46	9.182%	$239.6108	$239.61	$239.60	$239.60
Purchase #3	$212.34	4.560%	$222.0227	$222.02	$222.00	$222.00
Purchase #4	$201.63	4.286%	$210.2719	$210.27	$210.25	$210.30
Purchase #5	$95.32	10.435%	$105.2666	$105.27	$105.25	$105.30
Purchase #6	$34.35	13.693%	$39.0535	$39.05	$39.05	$39.10
Purchase #7	$119.59	9.199%	$130.5911	$130.59	$130.60	$130.60
7 purchase totals =	$988.07		$1,059.7334	$1,059.73	$1,059.65	$1,059.80