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	$222.80	13.276%	$252.3789	$252.38	$252.40	$252.40
Purchase #2	$69.28	4.805%	$72.6089	$72.61	$72.60	$72.60
Purchase #3	$222.65	9.349%	$243.4655	$243.47	$243.45	$243.50
Purchase #4	$162.73	3.612%	$168.6078	$168.61	$168.60	$168.60
Purchase #5	$180.36	4.755%	$188.9361	$188.94	$188.95	$188.90
Purchase #6	$137.95	7.784%	$148.688	$148.69	$148.70	$148.70
Purchase #7	$81.68	5.357%	$86.0556	$86.06	$86.05	$86.10
7 purchase totals =	$1,077.45		$1,160.7408	$1,160.76	$1,160.75	$1,160.80