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	$156.34	6.801%	$166.9727	$166.97	$166.95	$167.00
Purchase #2	$66.46	9.380%	$72.6939	$72.69	$72.70	$72.70
Purchase #3	$21.33	12.733%	$24.0459	$24.05	$24.05	$24.00
Purchase #4	$19.83	6.539%	$21.1267	$21.13	$21.15	$21.10
Purchase #5	$88.80	11.602%	$99.1026	$99.10	$99.10	$99.10
Purchase #6	$185.27	9.495%	$202.8614	$202.86	$202.85	$202.90
Purchase #7	$54.77	13.352%	$62.0829	$62.08	$62.10	$62.10
7 purchase totals =	$592.80		$648.8861	$648.88	$648.90	$648.90