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	$241.32	9.203%	$263.5287	$263.53	$263.55	$263.50
Purchase #2	$60.85	7.234%	$65.2519	$65.25	$65.25	$65.30
Purchase #3	$236.72	12.753%	$266.9089	$266.91	$266.90	$266.90
Purchase #4	$38.67	5.641%	$40.8514	$40.85	$40.85	$40.90
Purchase #5	$186.64	3.346%	$192.885	$192.89	$192.90	$192.90
Purchase #6	$221.82	6.539%	$236.3248	$236.32	$236.30	$236.30
Purchase #7	$82.99	7.273%	$89.0259	$89.03	$89.05	$89.00
7 purchase totals =	$1,069.01		$1,154.7766	$1,154.78	$1,154.80	$1,154.80