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	$131.73	10.692%	$145.8146	$145.81	$145.80	$145.80
Purchase #2	$45.54	6.233%	$48.3785	$48.38	$48.40	$48.40
Purchase #3	$83.83	6.870%	$89.5891	$89.59	$89.60	$89.60
Purchase #4	$230.39	13.325%	$261.0895	$261.09	$261.10	$261.10
Purchase #5	$240.72	12.124%	$269.9049	$269.90	$269.90	$269.90
Purchase #6	$196.99	7.454%	$211.6736	$211.67	$211.65	$211.70
Purchase #7	$168.97	3.121%	$174.2436	$174.24	$174.25	$174.20
7 purchase totals =	$1,098.17		$1,200.6938	$1,200.68	$1,200.70	$1,200.70