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	$159.87	4.359%	$166.8387	$166.84	$166.85	$166.80
Purchase #2	$48.82	12.202%	$54.777	$54.78	$54.80	$54.80
Purchase #3	$57.38	11.566%	$64.0166	$64.02	$64.00	$64.00
Purchase #4	$194.34	4.724%	$203.5206	$203.52	$203.50	$203.50
Purchase #5	$128.74	13.804%	$146.5113	$146.51	$146.50	$146.50
Purchase #6	$131.47	12.264%	$147.5935	$147.59	$147.60	$147.60
Purchase #7	$100.77	8.511%	$109.3465	$109.35	$109.35	$109.30
7 purchase totals =	$821.39		$892.6042	$892.61	$892.60	$892.50