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	$244.31	7.298%	$262.1397	$262.14	$262.15	$262.10
Purchase #2	$65.48	13.746%	$74.4809	$74.48	$74.50	$74.50
Purchase #3	$151.63	11.146%	$168.5307	$168.53	$168.55	$168.50
Purchase #4	$211.96	6.254%	$225.216	$225.22	$225.20	$225.20
Purchase #5	$208.90	7.533%	$224.6364	$224.64	$224.65	$224.60
Purchase #6	$103.69	12.856%	$117.0204	$117.02	$117.00	$117.00
Purchase #7	$27.35	4.742%	$28.6469	$28.65	$28.65	$28.60
7 purchase totals =	$1,013.32		$1,100.6710	$1,100.68	$1,100.70	$1,100.50