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	$141.51	4.153%	$147.3869	$147.39	$147.40	$147.40
Purchase #2	$224.97	5.222%	$236.7179	$236.72	$236.70	$236.70
Purchase #3	$176.50	8.333%	$191.2077	$191.21	$191.20	$191.20
Purchase #4	$72.88	13.730%	$82.8864	$82.89	$82.90	$82.90
Purchase #5	$187.30	6.475%	$199.4277	$199.43	$199.45	$199.40
Purchase #6	$169.88	5.514%	$179.2472	$179.25	$179.25	$179.20
Purchase #7	$70.88	9.328%	$77.4917	$77.49	$77.50	$77.50
7 purchase totals =	$1,043.92		$1,114.3655	$1,114.38	$1,114.40	$1,114.30