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	$150.77	10.335%	$166.3521	$166.35	$166.35	$166.40
Purchase #2	$38.76	9.646%	$42.4988	$42.50	$42.50	$42.50
Purchase #3	$164.87	10.546%	$182.2572	$182.26	$182.25	$182.30
Purchase #4	$146.64	12.115%	$164.4054	$164.41	$164.40	$164.40
Purchase #5	$67.38	6.178%	$71.5427	$71.54	$71.55	$71.50
Purchase #6	$196.62	13.546%	$223.2541	$223.25	$223.25	$223.30
Purchase #7	$227.83	7.273%	$244.4001	$244.40	$244.40	$244.40
7 purchase totals =	$992.87		$1,094.7104	$1,094.71	$1,094.70	$1,094.80