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	$243.71	9.584%	$267.0672	$267.07	$267.05	$267.10
Purchase #2	$124.50	13.236%	$140.9788	$140.98	$141.00	$141.00
Purchase #3	$158.25	7.144%	$169.5554	$169.56	$169.55	$169.60
Purchase #4	$230.47	13.446%	$261.459	$261.46	$261.45	$261.50
Purchase #5	$171.48	11.831%	$191.7678	$191.77	$191.75	$191.80
Purchase #6	$126.26	7.828%	$136.1436	$136.14	$136.15	$136.10
Purchase #7	$112.33	13.389%	$127.3699	$127.37	$127.35	$127.40
7 purchase totals =	$1,167.00		$1,294.3417	$1,294.35	$1,294.30	$1,294.50