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	$74.47	4.763%	$78.017	$78.02	$78.00	$78.00
Purchase #2	$164.76	10.664%	$182.33	$182.33	$182.35	$182.30
Purchase #3	$160.73	11.150%	$178.6514	$178.65	$178.65	$178.70
Purchase #4	$60.59	6.476%	$64.5138	$64.51	$64.50	$64.50
Purchase #5	$102.94	11.654%	$114.9366	$114.94	$114.95	$114.90
Purchase #6	$28.39	5.707%	$30.0102	$30.01	$30.00	$30.00
Purchase #7	$131.45	3.638%	$136.2322	$136.23	$136.25	$136.20
7 purchase totals =	$723.33		$784.6912	$784.69	$784.70	$784.60