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	$222.94	4.114%	$232.1118	$232.11	$232.10	$232.10
Purchase #2	$198.62	7.816%	$214.1441	$214.14	$214.15	$214.10
Purchase #3	$185.30	4.426%	$193.5014	$193.50	$193.50	$193.50
Purchase #4	$40.82	4.652%	$42.7189	$42.72	$42.70	$42.70
Purchase #5	$167.90	9.835%	$184.413	$184.41	$184.40	$184.40
Purchase #6	$72.37	11.660%	$80.8083	$80.81	$80.80	$80.80
Purchase #7	$116.78	12.458%	$131.3285	$131.33	$131.35	$131.30
7 purchase totals =	$1,004.73		$1,079.0260	$1,079.02	$1,079.00	$1,078.90