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	$56.84	8.129%	$61.4605	$61.46	$61.45	$61.50
Purchase #2	$156.93	5.479%	$165.5282	$165.53	$165.55	$165.50
Purchase #3	$215.35	5.612%	$227.4354	$227.44	$227.45	$227.40
Purchase #4	$193.54	9.309%	$211.5566	$211.56	$211.55	$211.60
Purchase #5	$101.97	3.272%	$105.3065	$105.31	$105.30	$105.30
Purchase #6	$179.30	10.620%	$198.3417	$198.34	$198.35	$198.30
Purchase #7	$27.49	7.211%	$29.4723	$29.47	$29.45	$29.50
7 purchase totals =	$931.42		$999.1012	$999.11	$999.10	$999.10