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	$143.56	8.567%	$155.8588	$155.86	$155.85	$155.90
Purchase #2	$18.45	8.512%	$20.0205	$20.02	$20.00	$20.00
Purchase #3	$241.51	7.230%	$258.9712	$258.97	$258.95	$259.00
Purchase #4	$156.64	3.501%	$162.124	$162.12	$162.10	$162.10
Purchase #5	$134.35	11.740%	$150.1227	$150.12	$150.10	$150.10
Purchase #6	$100.38	5.847%	$106.2492	$106.25	$106.25	$106.20
Purchase #7	$155.99	5.518%	$164.5975	$164.60	$164.60	$164.60
7 purchase totals =	$950.88		$1,017.9439	$1,017.94	$1,017.85	$1,017.90