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	$77.67	6.745%	$82.9088	$82.91	$82.90	$82.90
Purchase #2	$120.58	10.365%	$133.0781	$133.08	$133.10	$133.10
Purchase #3	$26.65	3.677%	$27.6299	$27.63	$27.65	$27.60
Purchase #4	$56.40	4.819%	$59.1179	$59.12	$59.10	$59.10
Purchase #5	$238.45	7.106%	$255.3943	$255.39	$255.40	$255.40
Purchase #6	$141.85	7.656%	$152.71	$152.71	$152.70	$152.70
Purchase #7	$139.39	9.799%	$153.0488	$153.05	$153.05	$153.00
7 purchase totals =	$800.99		$863.8878	$863.89	$863.90	$863.80