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	$150.31	9.547%	$164.6601	$164.66	$164.65	$164.70
Purchase #2	$144.53	12.591%	$162.7278	$162.73	$162.75	$162.70
Purchase #3	$108.97	7.474%	$117.1144	$117.11	$117.10	$117.10
Purchase #4	$77.31	4.174%	$80.5369	$80.54	$80.55	$80.50
Purchase #5	$242.86	7.455%	$260.9652	$260.97	$260.95	$261.00
Purchase #6	$111.93	10.689%	$123.8942	$123.89	$123.90	$123.90
Purchase #7	$136.49	4.322%	$142.3891	$142.39	$142.40	$142.40
7 purchase totals =	$972.40		$1,052.2877	$1,052.29	$1,052.30	$1,052.30