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	$182.86	3.580%	$189.4064	$189.41	$189.40	$189.40
Purchase #2	$64.36	11.798%	$71.9532	$71.95	$71.95	$72.00
Purchase #3	$175.66	13.214%	$198.8717	$198.87	$198.85	$198.90
Purchase #4	$91.52	12.450%	$102.9142	$102.91	$102.90	$102.90
Purchase #5	$59.90	10.423%	$66.1434	$66.14	$66.15	$66.10
Purchase #6	$59.76	3.620%	$61.9233	$61.92	$61.90	$61.90
Purchase #7	$103.72	6.362%	$110.3187	$110.32	$110.30	$110.30
7 purchase totals =	$737.78		$801.5309	$801.52	$801.45	$801.50