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	$179.80	8.235%	$194.6065	$194.61	$194.60	$194.60
Purchase #2	$110.55	6.625%	$117.8739	$117.87	$117.85	$117.90
Purchase #3	$91.93	5.577%	$97.0569	$97.06	$97.05	$97.10
Purchase #4	$182.30	7.518%	$196.0053	$196.01	$196.00	$196.00
Purchase #5	$67.96	11.663%	$75.8862	$75.89	$75.90	$75.90
Purchase #6	$90.92	10.658%	$100.6103	$100.61	$100.60	$100.60
Purchase #7	$220.88	3.372%	$228.3281	$228.33	$228.35	$228.30
7 purchase totals =	$944.34		$1,010.3672	$1,010.38	$1,010.35	$1,010.40