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	$119.60	4.873%	$125.4281	$125.43	$125.45	$125.40
Purchase #2	$185.65	7.357%	$199.3083	$199.31	$199.30	$199.30
Purchase #3	$60.70	4.535%	$63.4527	$63.45	$63.45	$63.50
Purchase #4	$224.72	6.148%	$238.5358	$238.54	$238.55	$238.50
Purchase #5	$86.78	5.761%	$91.7794	$91.78	$91.80	$91.80
Purchase #6	$80.54	11.104%	$89.4832	$89.48	$89.50	$89.50
Purchase #7	$86.99	12.719%	$98.0543	$98.05	$98.05	$98.10
7 purchase totals =	$844.98		$906.0418	$906.04	$906.10	$906.10