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	$79.33	3.692%	$82.2589	$82.26	$82.25	$82.30
Purchase #2	$236.31	12.378%	$265.5605	$265.56	$265.55	$265.60
Purchase #3	$6.62	9.145%	$7.2254	$7.23	$7.25	$7.20
Purchase #4	$115.36	7.212%	$123.6798	$123.68	$123.70	$123.70
Purchase #5	$86.82	5.799%	$91.8547	$91.85	$91.85	$91.90
Purchase #6	$116.45	8.561%	$126.4193	$126.42	$126.40	$126.40
Purchase #7	$44.52	4.694%	$46.6098	$46.61	$46.60	$46.60
7 purchase totals =	$685.41		$743.6084	$743.61	$743.60	$743.70