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	$15.37	7.768%	$16.5639	$16.56	$16.55	$16.60
Purchase #2	$76.69	7.285%	$82.2769	$82.28	$82.30	$82.30
Purchase #3	$72.82	12.109%	$81.6378	$81.64	$81.65	$81.60
Purchase #4	$190.35	5.284%	$200.4081	$200.41	$200.40	$200.40
Purchase #5	$84.43	10.578%	$93.361	$93.36	$93.35	$93.40
Purchase #6	$70.41	11.625%	$78.5952	$78.60	$78.60	$78.60
Purchase #7	$92.88	13.649%	$105.5572	$105.56	$105.55	$105.60
7 purchase totals =	$602.95		$658.4001	$658.41	$658.40	$658.50