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	$129.43	11.314%	$144.0737	$144.07	$144.05	$144.10
Purchase #2	$16.78	12.423%	$18.8646	$18.86	$18.85	$18.90
Purchase #3	$68.64	4.381%	$71.6471	$71.65	$71.65	$71.60
Purchase #4	$162.92	5.185%	$171.3674	$171.37	$171.35	$171.40
Purchase #5	$36.82	6.611%	$39.2542	$39.25	$39.25	$39.30
Purchase #6	$62.36	4.286%	$65.0327	$65.03	$65.05	$65.00
Purchase #7	$106.41	6.701%	$113.5405	$113.54	$113.55	$113.50
7 purchase totals =	$583.36		$623.7802	$623.77	$623.75	$623.80