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	$145.85	8.366%	$158.0518	$158.05	$158.05	$158.10
Purchase #2	$76.52	11.810%	$85.557	$85.56	$85.55	$85.60
Purchase #3	$193.83	3.531%	$200.6741	$200.67	$200.65	$200.70
Purchase #4	$116.82	8.624%	$126.8946	$126.89	$126.90	$126.90
Purchase #5	$88.27	10.786%	$97.7908	$97.79	$97.80	$97.80
Purchase #6	$148.77	12.818%	$167.8393	$167.84	$167.85	$167.80
Purchase #7	$78.47	13.468%	$89.0383	$89.04	$89.05	$89.00
7 purchase totals =	$848.53		$925.8459	$925.84	$925.85	$925.90