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	$219.30	6.651%	$233.8856	$233.89	$233.90	$233.90
Purchase #2	$142.43	13.759%	$162.0269	$162.03	$162.05	$162.00
Purchase #3	$73.75	13.796%	$83.9246	$83.92	$83.90	$83.90
Purchase #4	$186.80	5.174%	$196.465	$196.47	$196.45	$196.50
Purchase #5	$13.85	7.555%	$14.8964	$14.90	$14.90	$14.90
Purchase #6	$72.35	12.367%	$81.2975	$81.30	$81.30	$81.30
Purchase #7	$160.80	11.865%	$179.8789	$179.88	$179.90	$179.90
7 purchase totals =	$869.28		$952.3749	$952.39	$952.40	$952.40