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	$90.35	3.359%	$93.3849	$93.38	$93.40	$93.40
Purchase #2	$223.75	13.138%	$253.1463	$253.15	$253.15	$253.10
Purchase #3	$93.71	4.146%	$97.5952	$97.60	$97.60	$97.60
Purchase #4	$63.83	4.540%	$66.7279	$66.73	$66.75	$66.70
Purchase #5	$59.99	12.690%	$67.6027	$67.60	$67.60	$67.60
Purchase #6	$42.88	10.585%	$47.4188	$47.42	$47.40	$47.40
Purchase #7	$136.62	11.650%	$152.5362	$152.54	$152.55	$152.50
7 purchase totals =	$711.13		$778.4120	$778.42	$778.45	$778.30