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	$218.91	8.591%	$237.7166	$237.72	$237.70	$237.70
Purchase #2	$36.55	13.229%	$41.3852	$41.39	$41.40	$41.40
Purchase #3	$143.88	8.523%	$156.1429	$156.14	$156.15	$156.10
Purchase #4	$164.36	9.371%	$179.7622	$179.76	$179.75	$179.80
Purchase #5	$111.40	13.804%	$126.7777	$126.78	$126.80	$126.80
Purchase #6	$72.83	8.357%	$78.9164	$78.92	$78.90	$78.90
Purchase #7	$63.84	3.748%	$66.2327	$66.23	$66.25	$66.20
7 purchase totals =	$811.77		$886.9337	$886.94	$886.95	$886.90