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	$103.33	12.342%	$116.083	$116.08	$116.10	$116.10
Purchase #2	$53.27	12.477%	$59.9165	$59.92	$59.90	$59.90
Purchase #3	$62.91	7.571%	$67.6729	$67.67	$67.65	$67.70
Purchase #4	$143.28	3.268%	$147.9624	$147.96	$147.95	$148.00
Purchase #5	$63.62	7.217%	$68.2115	$68.21	$68.20	$68.20
Purchase #6	$167.30	7.506%	$179.8575	$179.86	$179.85	$179.90
Purchase #7	$118.87	4.161%	$123.8162	$123.82	$123.80	$123.80
7 purchase totals =	$712.58		$763.5200	$763.52	$763.45	$763.60