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	$136.52	4.404%	$142.5323	$142.53	$142.55	$142.50
Purchase #2	$16.68	7.705%	$17.9652	$17.97	$17.95	$18.00
Purchase #3	$65.75	9.565%	$72.039	$72.04	$72.05	$72.00
Purchase #4	$98.29	13.610%	$111.6673	$111.67	$111.65	$111.70
Purchase #5	$67.82	5.845%	$71.7841	$71.78	$71.80	$71.80
Purchase #6	$41.51	4.603%	$43.4207	$43.42	$43.40	$43.40
Purchase #7	$156.70	6.280%	$166.5408	$166.54	$166.55	$166.50
7 purchase totals =	$583.27		$625.9494	$625.95	$625.95	$625.90