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	$57.26	3.146%	$59.0614	$59.06	$59.05	$59.10
Purchase #2	$131.33	4.642%	$137.4263	$137.43	$137.45	$137.40
Purchase #3	$52.86	6.631%	$56.3651	$56.37	$56.35	$56.40
Purchase #4	$150.83	3.372%	$155.916	$155.92	$155.90	$155.90
Purchase #5	$15.70	8.529%	$17.0391	$17.04	$17.05	$17.00
Purchase #6	$191.55	3.506%	$198.2657	$198.27	$198.25	$198.30
Purchase #7	$43.34	8.158%	$46.8757	$46.88	$46.90	$46.90
7 purchase totals =	$642.87		$670.9493	$670.97	$670.95	$671.00