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	$105.96	3.874%	$110.0649	$110.06	$110.05	$110.10
Purchase #2	$144.89	13.333%	$164.2082	$164.21	$164.20	$164.20
Purchase #3	$144.28	4.107%	$150.2056	$150.21	$150.20	$150.20
Purchase #4	$92.96	3.258%	$95.9886	$95.99	$96.00	$96.00
Purchase #5	$80.26	10.384%	$88.5942	$88.59	$88.60	$88.60
Purchase #6	$83.27	13.582%	$94.5797	$94.58	$94.60	$94.60
Purchase #7	$123.85	12.615%	$139.4737	$139.47	$139.45	$139.50
7 purchase totals =	$775.47		$843.1149	$843.11	$843.10	$843.20