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	$150.64	13.539%	$171.0351	$171.04	$171.05	$171.00
Purchase #2	$79.54	7.220%	$85.2828	$85.28	$85.30	$85.30
Purchase #3	$204.77	3.698%	$212.3424	$212.34	$212.35	$212.30
Purchase #4	$49.88	3.116%	$51.4343	$51.43	$51.45	$51.40
Purchase #5	$68.56	6.378%	$72.9328	$72.93	$72.95	$72.90
Purchase #6	$170.34	10.628%	$188.4437	$188.44	$188.45	$188.40
Purchase #7	$13.66	9.874%	$15.0088	$15.01	$15.00	$15.00
7 purchase totals =	$737.39		$796.4799	$796.47	$796.55	$796.30