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	$29.68	11.250%	$33.019	$33.02	$33.00	$33.00
Purchase #2	$82.92	7.741%	$89.3388	$89.34	$89.35	$89.30
Purchase #3	$165.61	3.523%	$171.4444	$171.44	$171.45	$171.40
Purchase #4	$101.68	6.754%	$108.5475	$108.55	$108.55	$108.50
Purchase #5	$248.32	9.156%	$271.0562	$271.06	$271.05	$271.10
Purchase #6	$31.42	9.824%	$34.5067	$34.51	$34.50	$34.50
Purchase #7	$54.81	5.534%	$57.8432	$57.84	$57.85	$57.80
7 purchase totals =	$714.44		$765.7558	$765.76	$765.75	$765.60