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	$5.53	6.357%	$5.8815	$5.88	$5.90	$5.90
Purchase #2	$241.89	9.735%	$265.438	$265.44	$265.45	$265.40
Purchase #3	$82.76	13.873%	$94.2413	$94.24	$94.25	$94.20
Purchase #4	$190.70	4.795%	$199.8441	$199.84	$199.85	$199.80
Purchase #5	$37.95	12.741%	$42.7852	$42.79	$42.80	$42.80
Purchase #6	$214.73	10.346%	$236.946	$236.95	$236.95	$236.90
Purchase #7	$162.64	5.430%	$171.4714	$171.47	$171.45	$171.50
7 purchase totals =	$936.20		$1,016.6075	$1,016.61	$1,016.65	$1,016.50