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	$72.69	13.490%	$82.4959	$82.50	$82.50	$82.50
Purchase #2	$182.51	11.442%	$203.3928	$203.39	$203.40	$203.40
Purchase #3	$240.41	7.366%	$258.1186	$258.12	$258.10	$258.10
Purchase #4	$96.56	3.802%	$100.2312	$100.23	$100.25	$100.20
Purchase #5	$194.32	10.644%	$215.0034	$215.00	$215.00	$215.00
Purchase #6	$40.30	10.445%	$44.5093	$44.51	$44.50	$44.50
Purchase #7	$108.93	12.537%	$122.5866	$122.59	$122.60	$122.60
7 purchase totals =	$935.72		$1,026.3378	$1,026.34	$1,026.35	$1,026.30