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	$86.82	3.194%	$89.593	$89.59	$89.60	$89.60
Purchase #2	$105.78	7.813%	$114.0446	$114.04	$114.05	$114.00
Purchase #3	$188.37	13.605%	$213.9977	$214.00	$214.00	$214.00
Purchase #4	$166.77	3.490%	$172.5903	$172.59	$172.60	$172.60
Purchase #5	$6.69	11.224%	$7.4409	$7.44	$7.45	$7.40
Purchase #6	$39.27	9.395%	$42.9594	$42.96	$42.95	$43.00
Purchase #7	$243.36	13.667%	$276.62	$276.62	$276.60	$276.60
7 purchase totals =	$837.06		$917.2459	$917.24	$917.25	$917.20