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	$203.36	11.785%	$227.326	$227.33	$227.35	$227.30
Purchase #2	$29.68	4.739%	$31.0865	$31.09	$31.10	$31.10
Purchase #3	$203.75	9.164%	$222.4217	$222.42	$222.40	$222.40
Purchase #4	$162.56	3.394%	$168.0773	$168.08	$168.10	$168.10
Purchase #5	$156.41	3.771%	$162.3082	$162.31	$162.30	$162.30
Purchase #6	$96.28	7.698%	$103.6916	$103.69	$103.70	$103.70
Purchase #7	$119.50	12.552%	$134.4996	$134.50	$134.50	$134.50
7 purchase totals =	$971.54		$1,049.4109	$1,049.42	$1,049.45	$1,049.40