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	$171.30	8.763%	$186.311	$186.31	$186.30	$186.30
Purchase #2	$42.74	8.848%	$46.5216	$46.52	$46.50	$46.50
Purchase #3	$80.88	11.738%	$90.3737	$90.37	$90.35	$90.40
Purchase #4	$59.83	7.109%	$64.0833	$64.08	$64.10	$64.10
Purchase #5	$15.59	5.438%	$16.4378	$16.44	$16.45	$16.40
Purchase #6	$142.38	5.853%	$150.7135	$150.71	$150.70	$150.70
Purchase #7	$12.84	10.811%	$14.2281	$14.23	$14.25	$14.20
7 purchase totals =	$525.56		$568.6690	$568.66	$568.65	$568.60