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	$115.28	10.672%	$127.5827	$127.58	$127.60	$127.60
Purchase #2	$165.97	3.278%	$171.4105	$171.41	$171.40	$171.40
Purchase #3	$123.94	7.135%	$132.7831	$132.78	$132.80	$132.80
Purchase #4	$53.39	11.802%	$59.6911	$59.69	$59.70	$59.70
Purchase #5	$189.64	6.562%	$202.0842	$202.08	$202.10	$202.10
Purchase #6	$129.64	11.511%	$144.5629	$144.56	$144.55	$144.60
Purchase #7	$196.39	12.695%	$221.3217	$221.32	$221.30	$221.30
7 purchase totals =	$974.25		$1,059.4362	$1,059.42	$1,059.45	$1,059.50