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	$145.81	10.655%	$161.3461	$161.35	$161.35	$161.30
Purchase #2	$174.61	4.322%	$182.1566	$182.16	$182.15	$182.20
Purchase #3	$123.57	10.460%	$136.4954	$136.50	$136.50	$136.50
Purchase #4	$114.45	3.570%	$118.5359	$118.54	$118.55	$118.50
Purchase #5	$82.70	9.156%	$90.272	$90.27	$90.25	$90.30
Purchase #6	$123.76	3.474%	$128.0594	$128.06	$128.05	$128.10
Purchase #7	$226.57	13.264%	$256.6222	$256.62	$256.60	$256.60
7 purchase totals =	$991.47		$1,073.4876	$1,073.50	$1,073.45	$1,073.50