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	$175.56	8.288%	$190.1104	$190.11	$190.10	$190.10
Purchase #2	$44.92	13.575%	$51.0179	$51.02	$51.00	$51.00
Purchase #3	$186.59	5.231%	$196.3505	$196.35	$196.35	$196.40
Purchase #4	$74.52	11.752%	$83.2776	$83.28	$83.30	$83.30
Purchase #5	$187.76	8.662%	$204.0238	$204.02	$204.00	$204.00
Purchase #6	$238.56	11.348%	$265.6318	$265.63	$265.65	$265.60
Purchase #7	$88.90	13.823%	$101.1886	$101.19	$101.20	$101.20
7 purchase totals =	$996.81		$1,091.6006	$1,091.60	$1,091.60	$1,091.60