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	$112.56	6.130%	$119.4599	$119.46	$119.45	$119.50
Purchase #2	$181.49	10.462%	$200.4775	$200.48	$200.50	$200.50
Purchase #3	$10.53	3.681%	$10.9176	$10.92	$10.90	$10.90
Purchase #4	$94.47	3.492%	$97.7689	$97.77	$97.75	$97.80
Purchase #5	$242.85	10.623%	$268.648	$268.65	$268.65	$268.60
Purchase #6	$70.77	11.379%	$78.8229	$78.82	$78.80	$78.80
Purchase #7	$249.81	9.421%	$273.3446	$273.34	$273.35	$273.30
7 purchase totals =	$962.48		$1,049.4394	$1,049.44	$1,049.40	$1,049.40