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	$89.78	5.369%	$94.6003	$94.60	$94.60	$94.60
Purchase #2	$17.40	4.508%	$18.1844	$18.18	$18.20	$18.20
Purchase #3	$178.89	11.755%	$199.9185	$199.92	$199.90	$199.90
Purchase #4	$98.82	6.372%	$105.1168	$105.12	$105.10	$105.10
Purchase #5	$200.72	6.153%	$213.0703	$213.07	$213.05	$213.10
Purchase #6	$137.83	13.865%	$156.9401	$156.94	$156.95	$156.90
Purchase #7	$54.51	5.259%	$57.3767	$57.38	$57.40	$57.40
7 purchase totals =	$777.95		$845.2071	$845.21	$845.20	$845.20