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	$122.50	3.654%	$126.9762	$126.98	$127.00	$127.00
Purchase #2	$234.32	12.695%	$264.0669	$264.07	$264.05	$264.10
Purchase #3	$89.66	3.409%	$92.7165	$92.72	$92.70	$92.70
Purchase #4	$241.96	8.244%	$261.9072	$261.91	$261.90	$261.90
Purchase #5	$135.42	4.778%	$141.8904	$141.89	$141.90	$141.90
Purchase #6	$82.56	9.195%	$90.1514	$90.15	$90.15	$90.20
Purchase #7	$45.36	8.513%	$49.2215	$49.22	$49.20	$49.20
7 purchase totals =	$951.78		$1,026.9301	$1,026.94	$1,026.90	$1,027.00