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	$115.79	13.664%	$131.6115	$131.61	$131.60	$131.60
Purchase #2	$235.83	8.295%	$255.3921	$255.39	$255.40	$255.40
Purchase #3	$231.59	9.828%	$254.3507	$254.35	$254.35	$254.40
Purchase #4	$47.37	7.656%	$50.9966	$51.00	$51.00	$51.00
Purchase #5	$172.89	5.517%	$182.4283	$182.43	$182.45	$182.40
Purchase #6	$180.90	4.542%	$189.1165	$189.12	$189.10	$189.10
Purchase #7	$97.34	13.391%	$110.3748	$110.37	$110.35	$110.40
7 purchase totals =	$1,081.71		$1,174.2705	$1,174.27	$1,174.25	$1,174.30