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	$141.85	11.740%	$158.5032	$158.50	$158.50	$158.50
Purchase #2	$189.43	8.636%	$205.7892	$205.79	$205.80	$205.80
Purchase #3	$7.31	6.748%	$7.8033	$7.80	$7.80	$7.80
Purchase #4	$62.64	4.266%	$65.3122	$65.31	$65.30	$65.30
Purchase #5	$142.60	4.865%	$149.5375	$149.54	$149.55	$149.50
Purchase #6	$109.35	4.139%	$113.876	$113.88	$113.90	$113.90
Purchase #7	$246.65	5.300%	$259.7225	$259.72	$259.70	$259.70
7 purchase totals =	$899.83		$960.5439	$960.54	$960.55	$960.50