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	$52.98	3.160%	$54.6542	$54.65	$54.65	$54.70
Purchase #2	$172.74	5.859%	$182.8608	$182.86	$182.85	$182.90
Purchase #3	$86.87	9.310%	$94.9576	$94.96	$94.95	$95.00
Purchase #4	$96.56	7.591%	$103.8899	$103.89	$103.90	$103.90
Purchase #5	$118.98	3.784%	$123.4822	$123.48	$123.50	$123.50
Purchase #6	$160.59	13.354%	$182.0352	$182.04	$182.05	$182.00
Purchase #7	$71.28	13.149%	$80.6526	$80.65	$80.65	$80.70
7 purchase totals =	$760.00		$822.5325	$822.53	$822.55	$822.70