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	$96.66	3.513%	$100.0557	$100.06	$100.05	$100.10
Purchase #2	$145.96	8.281%	$158.0469	$158.05	$158.05	$158.00
Purchase #3	$46.82	13.275%	$53.0354	$53.04	$53.05	$53.00
Purchase #4	$33.52	8.443%	$36.3501	$36.35	$36.35	$36.40
Purchase #5	$72.46	4.737%	$75.8924	$75.89	$75.90	$75.90
Purchase #6	$165.43	12.403%	$185.9483	$185.95	$185.95	$185.90
Purchase #7	$10.38	11.334%	$11.5565	$11.56	$11.55	$11.60
7 purchase totals =	$571.23		$620.8853	$620.90	$620.90	$620.90