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	$244.80	12.527%	$275.4661	$275.47	$275.45	$275.50
Purchase #2	$167.82	11.431%	$187.0035	$187.00	$187.00	$187.00
Purchase #3	$218.55	11.801%	$244.3411	$244.34	$244.35	$244.30
Purchase #4	$182.45	3.631%	$189.0748	$189.07	$189.05	$189.10
Purchase #5	$155.60	10.222%	$171.5054	$171.51	$171.50	$171.50
Purchase #6	$102.47	11.498%	$114.252	$114.25	$114.25	$114.30
Purchase #7	$172.99	13.364%	$196.1084	$196.11	$196.10	$196.10
7 purchase totals =	$1,244.68		$1,377.7513	$1,377.75	$1,377.70	$1,377.80