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	$204.38	11.445%	$227.7713	$227.77	$227.75	$227.80
Purchase #2	$29.71	6.264%	$31.571	$31.57	$31.55	$31.60
Purchase #3	$87.88	8.736%	$95.5572	$95.56	$95.55	$95.60
Purchase #4	$90.28	10.302%	$99.5806	$99.58	$99.60	$99.60
Purchase #5	$203.65	7.651%	$219.2313	$219.23	$219.25	$219.20
Purchase #6	$14.31	12.180%	$16.053	$16.05	$16.05	$16.10
Purchase #7	$82.60	8.450%	$89.5797	$89.58	$89.60	$89.60
7 purchase totals =	$712.81		$779.3441	$779.34	$779.35	$779.50