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	$138.83	4.687%	$145.337	$145.34	$145.35	$145.30
Purchase #2	$246.41	10.590%	$272.5048	$272.50	$272.50	$272.50
Purchase #3	$128.26	5.873%	$135.7927	$135.79	$135.80	$135.80
Purchase #4	$66.77	5.620%	$70.5225	$70.52	$70.50	$70.50
Purchase #5	$180.87	13.676%	$205.6058	$205.61	$205.60	$205.60
Purchase #6	$78.80	4.179%	$82.0931	$82.09	$82.10	$82.10
Purchase #7	$137.56	11.120%	$152.8567	$152.86	$152.85	$152.90
7 purchase totals =	$977.50		$1,064.7126	$1,064.71	$1,064.70	$1,064.70