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	$171.82	6.113%	$182.3234	$182.32	$182.30	$182.30
Purchase #2	$168.69	13.590%	$191.615	$191.62	$191.60	$191.60
Purchase #3	$167.60	8.131%	$181.2276	$181.23	$181.25	$181.20
Purchase #4	$50.88	13.667%	$57.8338	$57.83	$57.85	$57.80
Purchase #5	$208.64	9.626%	$228.7237	$228.72	$228.70	$228.70
Purchase #6	$166.56	3.277%	$172.0182	$172.02	$172.00	$172.00
Purchase #7	$68.45	6.198%	$72.6925	$72.69	$72.70	$72.70
7 purchase totals =	$1,002.64		$1,086.4342	$1,086.43	$1,086.40	$1,086.30