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	$141.82	7.644%	$152.6607	$152.66	$152.65	$152.70
Purchase #2	$192.73	12.253%	$216.3452	$216.35	$216.35	$216.30
Purchase #3	$149.92	9.458%	$164.0994	$164.10	$164.10	$164.10
Purchase #4	$89.58	11.761%	$100.1155	$100.12	$100.10	$100.10
Purchase #5	$118.56	12.670%	$133.5816	$133.58	$133.60	$133.60
Purchase #6	$30.82	5.262%	$32.4417	$32.44	$32.45	$32.40
Purchase #7	$197.88	9.526%	$216.73	$216.73	$216.75	$216.70
7 purchase totals =	$921.31		$1,015.9741	$1,015.98	$1,016.00	$1,015.90