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	$70.82	11.361%	$78.8659	$78.87	$78.85	$78.90
Purchase #2	$220.69	4.856%	$231.4067	$231.41	$231.40	$231.40
Purchase #3	$150.89	9.520%	$165.2547	$165.25	$165.25	$165.30
Purchase #4	$42.69	7.735%	$45.9921	$45.99	$46.00	$46.00
Purchase #5	$199.46	8.180%	$215.7758	$215.78	$215.80	$215.80
Purchase #6	$91.82	5.757%	$97.1061	$97.11	$97.10	$97.10
Purchase #7	$162.94	7.382%	$174.9682	$174.97	$174.95	$175.00
7 purchase totals =	$939.31		$1,009.3695	$1,009.38	$1,009.35	$1,009.50