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	$240.72	7.830%	$259.5684	$259.57	$259.55	$259.60
Purchase #2	$38.29	7.318%	$41.0921	$41.09	$41.10	$41.10
Purchase #3	$109.33	6.555%	$116.4966	$116.50	$116.50	$116.50
Purchase #4	$92.52	13.445%	$104.9593	$104.96	$104.95	$105.00
Purchase #5	$147.44	13.694%	$167.6304	$167.63	$167.65	$167.60
Purchase #6	$223.82	8.775%	$243.4602	$243.46	$243.45	$243.50
Purchase #7	$27.69	12.526%	$31.1584	$31.16	$31.15	$31.20
7 purchase totals =	$879.81		$964.3654	$964.37	$964.35	$964.50