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	$118.54	7.280%	$127.1697	$127.17	$127.15	$127.20
Purchase #2	$38.35	10.113%	$42.2283	$42.23	$42.25	$42.20
Purchase #3	$219.70	5.222%	$231.1727	$231.17	$231.15	$231.20
Purchase #4	$128.77	9.535%	$141.0482	$141.05	$141.05	$141.00
Purchase #5	$149.55	12.855%	$168.7747	$168.77	$168.75	$168.80
Purchase #6	$154.74	13.235%	$175.2198	$175.22	$175.20	$175.20
Purchase #7	$248.47	8.806%	$270.3503	$270.35	$270.35	$270.40
7 purchase totals =	$1,058.12		$1,155.9637	$1,155.96	$1,155.90	$1,156.00