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	$166.40	13.637%	$189.092	$189.09	$189.10	$189.10
Purchase #2	$10.39	13.809%	$11.8248	$11.82	$11.80	$11.80
Purchase #3	$58.83	12.554%	$66.2155	$66.22	$66.20	$66.20
Purchase #4	$233.46	13.808%	$265.6962	$265.70	$265.70	$265.70
Purchase #5	$89.83	12.321%	$100.898	$100.90	$100.90	$100.90
Purchase #6	$222.88	12.596%	$250.954	$250.95	$250.95	$251.00
Purchase #7	$240.60	6.432%	$256.0754	$256.08	$256.10	$256.10
7 purchase totals =	$1,022.39		$1,140.7559	$1,140.76	$1,140.75	$1,140.80