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	$136.83	8.499%	$148.4592	$148.46	$148.45	$148.50
Purchase #2	$158.95	5.204%	$167.2218	$167.22	$167.20	$167.20
Purchase #3	$96.86	8.440%	$105.035	$105.04	$105.05	$105.00
Purchase #4	$64.34	13.264%	$72.8741	$72.87	$72.85	$72.90
Purchase #5	$102.91	12.789%	$116.0712	$116.07	$116.05	$116.10
Purchase #6	$169.55	12.550%	$190.8285	$190.83	$190.85	$190.80
Purchase #7	$222.31	12.444%	$249.9743	$249.97	$249.95	$250.00
7 purchase totals =	$951.75		$1,050.4641	$1,050.46	$1,050.40	$1,050.50