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	$64.63	10.815%	$71.6197	$71.62	$71.60	$71.60
Purchase #2	$107.40	11.204%	$119.4331	$119.43	$119.45	$119.40
Purchase #3	$43.40	5.719%	$45.882	$45.88	$45.90	$45.90
Purchase #4	$232.36	12.595%	$261.6257	$261.63	$261.65	$261.60
Purchase #5	$49.62	8.706%	$53.9399	$53.94	$53.95	$53.90
Purchase #6	$161.99	10.611%	$179.1788	$179.18	$179.20	$179.20
Purchase #7	$137.89	4.530%	$144.1364	$144.14	$144.15	$144.10
7 purchase totals =	$797.29		$875.8156	$875.82	$875.90	$875.70