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	$53.37	8.525%	$57.9198	$57.92	$57.90	$57.90
Purchase #2	$135.86	6.822%	$145.1284	$145.13	$145.15	$145.10
Purchase #3	$237.32	9.630%	$260.1739	$260.17	$260.15	$260.20
Purchase #4	$215.76	12.558%	$242.8551	$242.86	$242.85	$242.90
Purchase #5	$49.49	9.694%	$54.2876	$54.29	$54.30	$54.30
Purchase #6	$164.61	9.236%	$179.8134	$179.81	$179.80	$179.80
Purchase #7	$144.35	8.112%	$156.0597	$156.06	$156.05	$156.10
7 purchase totals =	$1,000.76		$1,096.2379	$1,096.24	$1,096.20	$1,096.30