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	$200.45	7.824%	$216.1332	$216.13	$216.15	$216.10
Purchase #2	$221.63	12.479%	$249.2872	$249.29	$249.30	$249.30
Purchase #3	$94.30	6.720%	$100.637	$100.64	$100.65	$100.60
Purchase #4	$134.57	7.276%	$144.3613	$144.36	$144.35	$144.40
Purchase #5	$196.37	9.849%	$215.7105	$215.71	$215.70	$215.70
Purchase #6	$109.57	9.668%	$120.1632	$120.16	$120.15	$120.20
Purchase #7	$155.56	7.725%	$167.577	$167.58	$167.60	$167.60
7 purchase totals =	$1,112.45		$1,213.8694	$1,213.87	$1,213.90	$1,213.90