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	$207.76	8.290%	$224.9833	$224.98	$225.00	$225.00
Purchase #2	$106.61	8.375%	$115.5386	$115.54	$115.55	$115.50
Purchase #3	$44.76	11.431%	$49.8765	$49.88	$49.90	$49.90
Purchase #4	$117.83	8.369%	$127.6912	$127.69	$127.70	$127.70
Purchase #5	$41.47	9.111%	$45.2483	$45.25	$45.25	$45.20
Purchase #6	$92.93	11.161%	$103.3019	$103.30	$103.30	$103.30
Purchase #7	$99.77	5.817%	$105.5736	$105.57	$105.55	$105.60
7 purchase totals =	$711.13		$772.2134	$772.21	$772.25	$772.20