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	$63.74	6.469%	$67.8633	$67.86	$67.85	$67.90
Purchase #2	$71.44	9.351%	$78.1204	$78.12	$78.10	$78.10
Purchase #3	$18.27	3.279%	$18.8691	$18.87	$18.85	$18.90
Purchase #4	$97.40	6.245%	$103.4826	$103.48	$103.50	$103.50
Purchase #5	$89.85	9.459%	$98.3489	$98.35	$98.35	$98.30
Purchase #6	$250.74	4.759%	$262.6727	$262.67	$262.65	$262.70
Purchase #7	$156.75	13.420%	$177.7859	$177.79	$177.80	$177.80
7 purchase totals =	$748.19		$807.1429	$807.14	$807.10	$807.20