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	$86.89	5.479%	$91.6507	$91.65	$91.65	$91.70
Purchase #2	$39.83	13.196%	$45.086	$45.09	$45.10	$45.10
Purchase #3	$134.75	7.234%	$144.4978	$144.50	$144.50	$144.50
Purchase #4	$19.49	8.704%	$21.1864	$21.19	$21.20	$21.20
Purchase #5	$107.92	4.305%	$112.566	$112.57	$112.55	$112.60
Purchase #6	$59.96	4.342%	$62.5635	$62.56	$62.55	$62.60
Purchase #7	$195.41	10.463%	$215.8557	$215.86	$215.85	$215.90
7 purchase totals =	$644.25		$693.4061	$693.42	$693.40	$693.60