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	$63.92	6.165%	$67.8607	$67.86	$67.85	$67.90
Purchase #2	$235.80	7.372%	$253.1832	$253.18	$253.20	$253.20
Purchase #3	$105.64	13.422%	$119.819	$119.82	$119.80	$119.80
Purchase #4	$43.55	6.847%	$46.5319	$46.53	$46.55	$46.50
Purchase #5	$72.77	12.423%	$81.8102	$81.81	$81.80	$81.80
Purchase #6	$232.99	4.184%	$242.7383	$242.74	$242.75	$242.70
Purchase #7	$98.72	4.860%	$103.5178	$103.52	$103.50	$103.50
7 purchase totals =	$853.39		$915.4611	$915.46	$915.45	$915.40