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	$118.40	3.661%	$122.7346	$122.73	$122.75	$122.70
Purchase #2	$189.59	5.665%	$200.3303	$200.33	$200.35	$200.30
Purchase #3	$64.27	4.346%	$67.0632	$67.06	$67.05	$67.10
Purchase #4	$120.42	13.168%	$136.2769	$136.28	$136.30	$136.30
Purchase #5	$177.47	9.397%	$194.1469	$194.15	$194.15	$194.10
Purchase #6	$72.29	8.540%	$78.4636	$78.46	$78.45	$78.50
Purchase #7	$237.38	8.191%	$256.8238	$256.82	$256.80	$256.80
7 purchase totals =	$979.82		$1,055.8393	$1,055.83	$1,055.85	$1,055.80