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	$231.58	10.230%	$255.2706	$255.27	$255.25	$255.30
Purchase #2	$55.41	7.121%	$59.3557	$59.36	$59.35	$59.40
Purchase #3	$126.27	5.446%	$133.1467	$133.15	$133.15	$133.10
Purchase #4	$75.80	7.604%	$81.5638	$81.56	$81.55	$81.60
Purchase #5	$83.85	13.453%	$95.1303	$95.13	$95.15	$95.10
Purchase #6	$202.55	5.534%	$213.7591	$213.76	$213.75	$213.80
Purchase #7	$204.86	5.801%	$216.7439	$216.74	$216.75	$216.70
7 purchase totals =	$980.32		$1,054.9701	$1,054.97	$1,054.95	$1,055.00