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	$33.95	3.373%	$35.0951	$35.10	$35.10	$35.10
Purchase #2	$117.30	6.781%	$125.2541	$125.25	$125.25	$125.30
Purchase #3	$166.85	7.244%	$178.9366	$178.94	$178.95	$178.90
Purchase #4	$19.66	6.258%	$20.8903	$20.89	$20.90	$20.90
Purchase #5	$132.43	3.360%	$136.8796	$136.88	$136.90	$136.90
Purchase #6	$150.64	10.639%	$166.6666	$166.67	$166.65	$166.70
Purchase #7	$188.45	4.289%	$196.5326	$196.53	$196.55	$196.50
7 purchase totals =	$809.28		$860.2549	$860.26	$860.30	$860.30