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	$246.66	7.121%	$264.2247	$264.22	$264.20	$264.20
Purchase #2	$65.96	9.241%	$72.0554	$72.06	$72.05	$72.10
Purchase #3	$41.59	5.379%	$43.8271	$43.83	$43.85	$43.80
Purchase #4	$116.47	9.214%	$127.2015	$127.20	$127.20	$127.20
Purchase #5	$98.78	12.719%	$111.3438	$111.34	$111.35	$111.30
Purchase #6	$161.83	3.791%	$167.965	$167.97	$167.95	$168.00
Purchase #7	$83.97	12.237%	$94.2454	$94.25	$94.25	$94.20
7 purchase totals =	$815.26		$880.8629	$880.87	$880.85	$880.80