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	$141.27	7.757%	$152.2283	$152.23	$152.25	$152.20
Purchase #2	$112.79	10.734%	$124.8969	$124.90	$124.90	$124.90
Purchase #3	$237.82	4.122%	$247.6229	$247.62	$247.60	$247.60
Purchase #4	$90.45	5.250%	$95.1986	$95.20	$95.20	$95.20
Purchase #5	$156.39	5.300%	$164.6787	$164.68	$164.70	$164.70
Purchase #6	$151.28	13.683%	$171.9796	$171.98	$172.00	$172.00
Purchase #7	$51.25	10.794%	$56.7819	$56.78	$56.80	$56.80
7 purchase totals =	$941.25		$1,013.3869	$1,013.39	$1,013.45	$1,013.40