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	$249.37	5.552%	$263.215	$263.22	$263.20	$263.20
Purchase #2	$57.90	12.363%	$65.0582	$65.06	$65.05	$65.10
Purchase #3	$77.67	8.705%	$84.4312	$84.43	$84.45	$84.40
Purchase #4	$186.90	7.217%	$200.3886	$200.39	$200.40	$200.40
Purchase #5	$114.35	5.322%	$120.4357	$120.44	$120.45	$120.40
Purchase #6	$141.76	3.294%	$146.4296	$146.43	$146.45	$146.40
Purchase #7	$208.95	9.869%	$229.5713	$229.57	$229.55	$229.60
7 purchase totals =	$1,036.90		$1,109.5296	$1,109.54	$1,109.55	$1,109.50