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	$101.53	3.529%	$105.113	$105.11	$105.10	$105.10
Purchase #2	$120.34	3.471%	$124.517	$124.52	$124.50	$124.50
Purchase #3	$243.92	12.179%	$273.627	$273.63	$273.65	$273.60
Purchase #4	$123.50	3.665%	$128.0263	$128.03	$128.05	$128.00
Purchase #5	$176.94	9.427%	$193.6201	$193.62	$193.60	$193.60
Purchase #6	$42.43	7.354%	$45.5503	$45.55	$45.55	$45.60
Purchase #7	$11.59	4.611%	$12.1244	$12.12	$12.10	$12.10
7 purchase totals =	$820.25		$882.5781	$882.58	$882.55	$882.50