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	$162.49	9.287%	$177.5804	$177.58	$177.60	$177.60
Purchase #2	$40.49	13.158%	$45.8177	$45.82	$45.80	$45.80
Purchase #3	$159.76	8.499%	$173.338	$173.34	$173.35	$173.30
Purchase #4	$49.53	11.819%	$55.384	$55.38	$55.40	$55.40
Purchase #5	$148.51	13.548%	$168.6301	$168.63	$168.65	$168.60
Purchase #6	$84.28	6.140%	$89.4548	$89.45	$89.45	$89.50
Purchase #7	$72.55	7.746%	$78.1697	$78.17	$78.15	$78.20
7 purchase totals =	$717.61		$788.3747	$788.37	$788.40	$788.40