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	$239.55	10.590%	$264.9183	$264.92	$264.90	$264.90
Purchase #2	$156.94	3.744%	$162.8158	$162.82	$162.80	$162.80
Purchase #3	$46.50	7.185%	$49.841	$49.84	$49.85	$49.80
Purchase #4	$27.59	6.505%	$29.3847	$29.38	$29.40	$29.40
Purchase #5	$220.66	12.773%	$248.8449	$248.84	$248.85	$248.80
Purchase #6	$152.86	5.234%	$160.8607	$160.86	$160.85	$160.90
Purchase #7	$172.38	6.116%	$182.9228	$182.92	$182.90	$182.90
7 purchase totals =	$1,016.48		$1,099.5882	$1,099.58	$1,099.55	$1,099.50