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	$104.50	6.586%	$111.3824	$111.38	$111.40	$111.40
Purchase #2	$53.46	7.807%	$57.6336	$57.63	$57.65	$57.60
Purchase #3	$104.78	7.422%	$112.5568	$112.56	$112.55	$112.60
Purchase #4	$34.51	9.274%	$37.7105	$37.71	$37.70	$37.70
Purchase #5	$182.59	5.661%	$192.9264	$192.93	$192.95	$192.90
Purchase #6	$101.56	13.482%	$115.2523	$115.25	$115.25	$115.30
Purchase #7	$71.36	6.302%	$75.8571	$75.86	$75.85	$75.90
7 purchase totals =	$652.76		$703.3191	$703.32	$703.35	$703.40