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	$93.27	5.132%	$98.0566	$98.06	$98.05	$98.10
Purchase #2	$133.39	12.818%	$150.4879	$150.49	$150.50	$150.50
Purchase #3	$116.83	9.767%	$128.2408	$128.24	$128.25	$128.20
Purchase #4	$183.93	6.577%	$196.0271	$196.03	$196.05	$196.00
Purchase #5	$145.60	6.814%	$155.5212	$155.52	$155.50	$155.50
Purchase #6	$28.49	10.653%	$31.525	$31.53	$31.55	$31.50
Purchase #7	$148.91	9.338%	$162.8152	$162.82	$162.80	$162.80
7 purchase totals =	$850.42		$922.6738	$922.69	$922.70	$922.60