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	$141.68	6.508%	$150.9005	$150.90	$150.90	$150.90
Purchase #2	$35.32	7.792%	$38.0721	$38.07	$38.05	$38.10
Purchase #3	$33.83	9.641%	$37.0916	$37.09	$37.10	$37.10
Purchase #4	$19.64	3.438%	$20.3152	$20.32	$20.30	$20.30
Purchase #5	$188.88	12.498%	$212.4862	$212.49	$212.50	$212.50
Purchase #6	$12.76	7.629%	$13.7335	$13.73	$13.75	$13.70
Purchase #7	$115.26	9.550%	$126.2673	$126.27	$126.25	$126.30
7 purchase totals =	$547.37		$598.8664	$598.87	$598.85	$598.90