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	$59.64	5.721%	$63.052	$63.05	$63.05	$63.10
Purchase #2	$86.62	3.421%	$89.5833	$89.58	$89.60	$89.60
Purchase #3	$93.93	10.742%	$104.02	$104.02	$104.00	$104.00
Purchase #4	$85.31	7.342%	$91.5735	$91.57	$91.55	$91.60
Purchase #5	$42.64	9.822%	$46.8281	$46.83	$46.85	$46.80
Purchase #6	$80.82	3.266%	$83.4596	$83.46	$83.45	$83.50
Purchase #7	$180.63	5.499%	$190.5628	$190.56	$190.55	$190.60
7 purchase totals =	$629.59		$669.0793	$669.07	$669.05	$669.20