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	$94.60	3.872%	$98.2629	$98.26	$98.25	$98.30
Purchase #2	$78.56	8.570%	$85.2926	$85.29	$85.30	$85.30
Purchase #3	$89.84	5.572%	$94.8459	$94.85	$94.85	$94.80
Purchase #4	$234.81	11.347%	$261.4539	$261.45	$261.45	$261.50
Purchase #5	$140.31	12.521%	$157.8782	$157.88	$157.90	$157.90
Purchase #6	$41.76	10.246%	$46.0387	$46.04	$46.05	$46.00
Purchase #7	$244.85	5.405%	$258.0841	$258.08	$258.10	$258.10
7 purchase totals =	$924.73		$1,001.8563	$1,001.85	$1,001.90	$1,001.90