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	$14.76	13.432%	$16.7426	$16.74	$16.75	$16.70
Purchase #2	$181.86	3.799%	$188.7689	$188.77	$188.75	$188.80
Purchase #3	$29.30	7.490%	$31.4946	$31.49	$31.50	$31.50
Purchase #4	$132.67	10.424%	$146.4995	$146.50	$146.50	$146.50
Purchase #5	$73.33	13.757%	$83.418	$83.42	$83.40	$83.40
Purchase #6	$6.85	6.727%	$7.3108	$7.31	$7.30	$7.30
Purchase #7	$145.64	5.242%	$153.2744	$153.27	$153.25	$153.30
7 purchase totals =	$584.41		$627.5088	$627.50	$627.45	$627.50