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	$198.38	13.858%	$225.8715	$225.87	$225.85	$225.90
Purchase #2	$108.37	11.550%	$120.8867	$120.89	$120.90	$120.90
Purchase #3	$42.93	5.832%	$45.4337	$45.43	$45.45	$45.40
Purchase #4	$195.71	12.566%	$220.3029	$220.30	$220.30	$220.30
Purchase #5	$192.45	12.195%	$215.9193	$215.92	$215.90	$215.90
Purchase #6	$22.72	11.782%	$25.3969	$25.40	$25.40	$25.40
Purchase #7	$141.38	4.378%	$147.5696	$147.57	$147.55	$147.60
7 purchase totals =	$901.94		$1,001.3806	$1,001.38	$1,001.35	$1,001.40