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	$200.93	8.453%	$217.9146	$217.91	$217.90	$217.90
Purchase #2	$188.87	6.170%	$200.5233	$200.52	$200.50	$200.50
Purchase #3	$168.37	4.874%	$176.5764	$176.58	$176.60	$176.60
Purchase #4	$7.57	8.819%	$8.2376	$8.24	$8.25	$8.20
Purchase #5	$41.68	9.382%	$45.5904	$45.59	$45.60	$45.60
Purchase #6	$120.32	5.840%	$127.3467	$127.35	$127.35	$127.30
Purchase #7	$245.86	6.180%	$261.0541	$261.05	$261.05	$261.10
7 purchase totals =	$973.60		$1,037.2431	$1,037.24	$1,037.25	$1,037.20