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	$111.74	13.872%	$127.2406	$127.24	$127.25	$127.20
Purchase #2	$208.93	8.431%	$226.5449	$226.54	$226.55	$226.50
Purchase #3	$101.30	4.705%	$106.0662	$106.07	$106.05	$106.10
Purchase #4	$233.79	10.797%	$259.0323	$259.03	$259.05	$259.00
Purchase #5	$90.57	12.258%	$101.6721	$101.67	$101.65	$101.70
Purchase #6	$238.86	10.707%	$264.4347	$264.43	$264.45	$264.40
Purchase #7	$44.55	5.231%	$46.8804	$46.88	$46.90	$46.90
7 purchase totals =	$1,029.74		$1,131.8712	$1,131.86	$1,131.90	$1,131.80