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	$14.33	11.783%	$16.0185	$16.02	$16.00	$16.00
Purchase #2	$59.44	4.753%	$62.2652	$62.27	$62.25	$62.30
Purchase #3	$67.61	7.245%	$72.5083	$72.51	$72.50	$72.50
Purchase #4	$227.45	5.585%	$240.1531	$240.15	$240.15	$240.20
Purchase #5	$80.71	11.366%	$89.8835	$89.88	$89.90	$89.90
Purchase #6	$83.63	3.205%	$86.3103	$86.31	$86.30	$86.30
Purchase #7	$179.39	10.713%	$198.6081	$198.61	$198.60	$198.60
7 purchase totals =	$712.56		$765.7470	$765.75	$765.70	$765.80