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	$249.61	4.279%	$260.2908	$260.29	$260.30	$260.30
Purchase #2	$16.81	4.503%	$17.567	$17.57	$17.55	$17.60
Purchase #3	$65.57	9.549%	$71.8313	$71.83	$71.85	$71.80
Purchase #4	$67.89	6.842%	$72.535	$72.54	$72.55	$72.50
Purchase #5	$157.34	4.420%	$164.2944	$164.29	$164.30	$164.30
Purchase #6	$179.40	10.840%	$198.847	$198.85	$198.85	$198.80
Purchase #7	$240.95	11.672%	$269.0737	$269.07	$269.05	$269.10
7 purchase totals =	$977.57		$1,054.4392	$1,054.44	$1,054.45	$1,054.40