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	$141.25	10.591%	$156.2098	$156.21	$156.20	$156.20
Purchase #2	$40.52	3.786%	$42.0541	$42.05	$42.05	$42.10
Purchase #3	$91.75	6.258%	$97.4917	$97.49	$97.50	$97.50
Purchase #4	$146.33	13.782%	$166.4972	$166.50	$166.50	$166.50
Purchase #5	$94.86	3.465%	$98.1469	$98.15	$98.15	$98.10
Purchase #6	$123.91	13.533%	$140.6787	$140.68	$140.70	$140.70
Purchase #7	$114.28	8.768%	$124.3001	$124.30	$124.30	$124.30
7 purchase totals =	$752.90		$825.3785	$825.38	$825.40	$825.40