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	$208.89	5.672%	$220.7382	$220.74	$220.75	$220.70
Purchase #2	$248.97	12.186%	$279.3095	$279.31	$279.30	$279.30
Purchase #3	$174.82	12.543%	$196.7477	$196.75	$196.75	$196.70
Purchase #4	$196.37	9.829%	$215.6712	$215.67	$215.65	$215.70
Purchase #5	$236.60	5.476%	$249.5562	$249.56	$249.55	$249.60
Purchase #6	$208.52	4.469%	$217.8388	$217.84	$217.85	$217.80
Purchase #7	$34.55	7.764%	$37.2325	$37.23	$37.25	$37.20
7 purchase totals =	$1,308.72		$1,417.0941	$1,417.10	$1,417.10	$1,417.00