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	$9.73	13.352%	$11.0291	$11.03	$11.05	$11.00
Purchase #2	$213.89	10.133%	$235.5635	$235.56	$235.55	$235.60
Purchase #3	$58.73	9.386%	$64.2424	$64.24	$64.25	$64.20
Purchase #4	$166.38	13.314%	$188.5318	$188.53	$188.55	$188.50
Purchase #5	$54.75	9.445%	$59.9211	$59.92	$59.90	$59.90
Purchase #6	$108.26	5.803%	$114.5423	$114.54	$114.55	$114.50
Purchase #7	$33.61	7.632%	$36.1751	$36.18	$36.20	$36.20
7 purchase totals =	$645.35		$710.0053	$710.00	$710.05	$709.90