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	$158.39	5.819%	$167.6067	$167.61	$167.60	$167.60
Purchase #2	$90.38	13.149%	$102.2641	$102.26	$102.25	$102.30
Purchase #3	$67.38	7.798%	$72.6343	$72.63	$72.65	$72.60
Purchase #4	$227.64	8.115%	$246.113	$246.11	$246.10	$246.10
Purchase #5	$167.47	13.169%	$189.5241	$189.52	$189.50	$189.50
Purchase #6	$222.39	12.289%	$249.7195	$249.72	$249.70	$249.70
Purchase #7	$203.36	5.460%	$214.4635	$214.46	$214.45	$214.50
7 purchase totals =	$1,137.01		$1,242.3252	$1,242.31	$1,242.25	$1,242.30