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	$134.59	4.126%	$140.1432	$140.14	$140.15	$140.10
Purchase #2	$201.27	4.229%	$209.7817	$209.78	$209.80	$209.80
Purchase #3	$127.77	12.666%	$143.9533	$143.95	$143.95	$144.00
Purchase #4	$54.37	9.692%	$59.6395	$59.64	$59.65	$59.60
Purchase #5	$99.81	8.221%	$108.0154	$108.02	$108.00	$108.00
Purchase #6	$214.49	7.462%	$230.4952	$230.50	$230.50	$230.50
Purchase #7	$204.33	4.398%	$213.3164	$213.32	$213.30	$213.30
7 purchase totals =	$1,036.63		$1,105.3447	$1,105.35	$1,105.35	$1,105.30