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	$41.96	8.625%	$45.5791	$45.58	$45.60	$45.60
Purchase #2	$19.51	3.227%	$20.1396	$20.14	$20.15	$20.10
Purchase #3	$149.96	9.415%	$164.0787	$164.08	$164.10	$164.10
Purchase #4	$104.98	6.584%	$111.8919	$111.89	$111.90	$111.90
Purchase #5	$170.72	6.804%	$182.3358	$182.34	$182.35	$182.30
Purchase #6	$132.78	12.262%	$149.0615	$149.06	$149.05	$149.10
Purchase #7	$170.47	4.744%	$178.5571	$178.56	$178.55	$178.60
7 purchase totals =	$790.38		$851.6437	$851.65	$851.70	$851.70